Visual Memory

In subject area: Neuroscience

Definition of topic

AI

Visual memory is defined as the relationship between perceptual processing and the storage and retrieval of neural representations of visual images. It involves the retention of memories related to visual stimuli, such as images and patterns.

AI generated definition based on: Psychiatry Research, 2014

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Topic summaryAI

1. Introduction to Visual Memory in Neuroscience

Visual memory is the cognitive function that enables the encoding, storage, and retrieval of visual information. It encompasses both the memory of any information viewed by the eye and not available to other senses, and a special code wherein information is stored by the brain in terms of images or sequences of images. The concept includes two related meanings: it refers either to the memory of any kind of information perceived visually, or to a code by which visual perceptions are inscribed and retrieved from memory in the form of images. Visual memory is not a separate memory system but a representation of information processed by different memory systems, and what is viewed by the eye may be stored amodally, such as in systems relying on verbal codes.

Evidence from animal research, studies of patients with focal brain lesions, and modern brain imaging experiments demonstrates that visual codes are important in memory, and that visual perception and visual memory processes are closely interwoven. Visual memory recruits many of the brain areas involved in online perception, indicating a close relationship between visual perception and visual memory processes.

Visual memory is supported by multiple coding principles, including both visual and verbal representations. Modern research confirms that visual memory is superior to other forms of memory, being able to store vast amounts of information in terms of pictures or natural scenes.

2. Neural Substrates and Mechanisms of Visual Memory

The occipital lobe, including the primary visual cortex (area V1) and extrastriate areas, is responsible for early visual processing. The occipital extrastriate cortex (Brodmann area 19) is consistently engaged during short-term memory for spatial location. The occipital and temporal regions participate in perceptual analysis, while the posterior parietal cortex computes stimulus coordinates and the premotor and prefrontal cortices are involved in storage and rehearsal.

The inferior temporal (IT) cortex, located in the temporal lobe, is a key site for visual long-term memory storage and associative memory. Neuronal correlates of long-term memory have been identified in the anterior ventral IT cortex, with pair-coding neurons exhibiting correlated visual responses to picture pairs in associative tasks. Lesions in the IT cortex produce deficits in visual recognition memory, and the perirhinal cortex is involved in retrieval of visual long-term memory. The posterior inferior temporal cortex is activated during visual recall and learning tasks, suggesting its role as a remote visual association area.

The hippocampus and medial temporal lobe are central to episodic visual memory and memory reinstatement. The medial temporal lobe receives information from different modalities and is involved in retrieval of visual long-term memory.

The parietal cortex, particularly the posterior–inferior parietal regions (Brodmann area 40), is involved in spatial aspects of visual memory. Short-term memory for spatial locations is disrupted by damage to the posterior parieto-occipital regions, with right hemisphere damage being more relevant for spatial memory. The dorsal visual stream is associated with short-term memory for spatial locations, while the ventral stream is linked to recognition memory for visual patterns.

The prefrontal cortex, including dorsolateral and ventrolateral areas, is implicated in working memory maintenance, executive control, and retrieval processes. Dorsolateral prefrontal areas are associated with short-term memory for spatial location, and ventral areas with short-term memory for patterns. The prefrontal cortex is involved in rehearsal and retention processes, with bilateral activation observed, but more sustained activity in the right hemisphere for spatial memory and in the left for visual pattern recognition.

Hemispheric lateralization is evident, with right hemisphere dominance for spatial memory and left hemisphere involvement in visual pattern recognition and verbal or symbolic encoding of visual objects. Visual memories are hemispherically organized, with an accuracy advantage when stimuli are re-presented to the same hemifield as initial encoding.

Visual memory traces are distributed across sensory and associative areas, and lateralized adaptation effects are observed in regions contralateral to the encoding side. Memory researchers generally agree that memories may involve many of the neural ensembles that were involved in the processing of the information in the first place.

3. Types and Functional Characteristics of Visual Memory

Iconic memory is a very short-term image store that holds what is on the retina until it is replaced by new input or until several hundred milliseconds have passed, and this information is image-related and lacks semantic content. Visual working memory is a system used to actively store and manipulate visual information, and is severely limited in capacity. The visual–spatial sketchpad, a support system within visual working memory, integrates information from visual, tactile, and haptic sensory channels, and is comparable to visual imagery, though maintenance in visual working memory is not conceived as a conscious process in the same sense as visual imagery. Visual imagery is disrupted by task-irrelevant visual noise, whereas maintenance in visual working memory is not disrupted by visual noise, indicating a distinction between these processes. Visual working memory typically retains the shape, color, texture, and location of about three to five simple objects, with the exact number depending on the task and pattern complexity. Meaningfulness, knowledge, and familiarity play an important role in visual working memory and in shaping its capacity, with stimuli that form meaningful units or have learned associations allowing for greater performance in visual working memory.

In the context of scene memory and memory reinstatement, eye movements provide spatiotemporal information about memory processing, and fixation reinstatement serves as a behavioral measure of memory reinstatement. Theories of visual memory propose that the sequence of eye movements becomes incorporated into memory during encoding, and memory recall involves reinstatement of the same sequence of eye movements; successful scene retrieval is marked by such reinstatement, and neural reinstatement positively correlates with fixation reinstatement.

The multiple-coding principle of visual memory states that information entering the brain through the eyes can be stored and remembered in terms of visual representations—images and sequences of images—or recoded and stored by the brain in terms of verbal or categorical representations. This principle is part of the explanation for why long-term visual memory generally outperforms other forms of memory.

4. Methods and Experimental Approaches to Study Visual Memory

Neuroimaging techniques such as functional magnetic resonance imaging (fMRI) are used to map brain activity during the encoding, maintenance, and retrieval phases of visual memory tasks, revealing activation in extrastriate cortical regions, temporal lobe, hippocampus, and ventrolateral prefrontal cortex during visual working memory and long-term memory processes. Single-unit electrophysiological recordings in nonhuman primates have identified neuronal correlates of visual memory in the inferior temporal cortex, with specific neurons in the anterior ventral inferior temporal cortex exhibiting correlated responses to paired visual stimuli. Lesion and neuropsychological studies examine deficits in patients with focal brain damage, such as posterior cerebral artery (PCA) infarcts, temporal lobectomy, and thalamic lesions, to infer the functional roles of brain regions in visual memory, with findings indicating that right PCA infarcts impair visual memory.

Behavioral paradigms include the delayed matching-to-sample task, visual paired-comparison, and recognition memory tests, which assess the ability to retain and recall visual information over short and long intervals. Transcranial Magnetic Stimulation (TMS) and Transcranial Direct Current Stimulation (tDCS) are used to causally probe and modulate visual memory processes; TMS over occipital cortex can disrupt or reactivate visual memory content, induce phosphenes, and alter memory retention, while tDCS over temporal and parietal regions can enhance or impair visual memory performance depending on stimulation parameters.

Interpreting results from these approaches requires consideration of the distributed and overlapping nature of memory networks, as visual memory processes often involve coordinated activity across multiple brain regions.

5. Visual Memory Impairments and Clinical Relevance

Amnesic syndromes following posterior cerebral artery (PCA) infarcts can result in visual amnesic syndromes due to disconnection between occipital cortices and temporal regions supporting memory, with right PCA infarcts causing impaired visual memory and left PCA infarcts leading to verbal memory deficits. Thalamic lesions, particularly those affecting the mammillo–thalamic tract, are associated with severe anterograde amnesia, and right-sided thalamic lesions result in nonverbal/visual memory impairments. Wernicke–Korsakoff syndrome, arising from thalamic nuclei and mammillary body damage, produces dense amnesia affecting both anterograde and retrograde memory, with episodic memory impairment explained by deficits in encoding and retrieval processes.

Visual agnosias are classified as apperceptive, where patients cannot construct perceptual representations, and associative, where meaning cannot be linked to visual input; associative agnosia is often due to bilateral medial inferior occipitotemporal lesions disrupting the inferior longitudinal fasciculus. Prosopagnosia, the inability to recognize familiar faces, is typically associated with occipitotemporal lesions and may co-occur with visual object agnosia and alexia without agraphia. Optic aphasia is characterized by inability to name visually presented objects despite intact object knowledge, often linked to left PCA territory infarction.

Alzheimer’s disease (AD) is associated with progressive visual memory and perceptual deficits, including impaired visual acuity, visual field defects, dyschromatopsia, and decreased contrast sensitivity, attributed to neurodegeneration in both afferent and cortical visual pathways. Visual object agnosia and prosopagnosia are frequently observed in AD, with pathology involving the occipitoparietal and occipitotemporal areas. Performance on visual memory tests, such as the Benton Visual Retention Test, is predictive of AD development years before diagnosis.

Neuropsychological evidence demonstrates dissociation between visual memory and other forms of memory, with cases showing preserved perception but impaired visual memory or recognition, as in visual agnosia. Deficits in visual working memory and spatial memory can disrupt object recognition, spatial navigation, and daily functioning, as seen in Bálint syndrome and AD. Visual memory impairments may manifest as difficulties in recognizing objects, faces, and spatial locations, affecting independence and daily activities. Retraining in visuospatial perception and coordination can be carried out by the use of computerized programs, particularly in patients with right-hemisphere damage or dysfunction, traumatic brain injury, or occipital–parietal–temporal lobe lesions. Acetylcholinesterase inhibitors may facilitate central visual processing in Alzheimer’s disease.

6. Conclusion and Future Directions

Visual memory is recognized as a distributed cognitive function that recruits many of the brain areas involved in online perception, with processes of visual perception and visual memory closely interwoven. Functional magnetic resonance imaging and positron emission tomography studies have shown that distinct regions localized to the occipital and temporal lobes are activated in visual memory tasks, and that memory involves widely distributed networks across the cerebral cortex. The neural basis of visual memory is investigated through behavioral, neuroimaging, electrophysiological, and stimulation studies, which together reveal that memories may involve neural ensembles originally engaged during perception.

Emerging research highlights the role of early visual cortex in memory retention and imagery, with some studies claiming activation of primary visual cortex (area V1) during visual memory tasks, though the extent of this involvement remains debated. Transcranial magnetic stimulation studies have shown that visual memory in early visual cortex is topographically organized and capacity-limited, and that short-term consolidation occurs early during retention. The overlap between visual imagery and perception is further supported by evidence that visual imagery and visual memory share functional resources from early visual cortices.

Neural dynamics of memory reinstatement and internal coupling are explored through studies of eye movements and oscillatory activity, with findings indicating that memory retrieval involves reinstatement of neural activity present during initial encoding, and that eye-movement behaviors provide behavioral measures of memory reinstatement.

Advances in brain stimulation techniques, including transcranial magnetic stimulation and photobiomodulation, have demonstrated the ability to modulate visual memory and improve performance in clinical populations.

References (41)

Reference 1
Reference works Chapter
Visual Memory, Psychology of
S. Magnussen
International Encyclopedia of the Social & Behavioral Sciences , 2001 pp 16264-16266
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"... The concept of visual memory has two related meanings in the literature, referring either to the memory of any kind of information viewed by the eye and not available to other senses, or to a special code wherein information is stored by the brain in terms of images. Evidence from animal research, studies of patients with focal brain lesions, and modern brain imaging experiments demonstrate that visual codes are important in memory, and that visual perception and visual memory processes are closely interwoven. ..."
Related quote(s)2 / 4
"... Visual Memory as a Code In a more restricted usage, visual memory refers to a code by which visual perceptions are inscribed and retrieved from memory in the form of images or sequences of images. According to this definition, visual memory is not a separate memory system but a representation of information that is processed by different memory systems. This definition also acknowledges that the channel of communication does not specify the memory format; what is viewed by the eye may be stored amodally, e.g., in memory systems relying on verbal codes. 2.1 Object Recognition A direct expression of visual memory is the perceptual process itself, in the recognition of colors, textures, shapes, and objects in the world. This is achieved by some process by which on-line information from the visual system is matched to stored descriptions. Perceptual recognition is immediate, representing a fast, automatic and implicit (nonconscious) process (see Implicit Memory, Cognitive Psychology of ), and it precedes semantic and episodic memory retrieval which deal with the identification of particular, familiar objects. The vast collection of memories that allow perceptual recognition is at least partly associated with a separate memory system, called the perceptual representation system (PRS) . The PRS was formally proposed as a separate memory system in 1990, and is currently under intense investigation. It is believed to consist of several subsystems, one of which is a structural description system which stores descriptions of coherent or meaningful objects. A more recent theoretical proposal identifies a series of specialized memory processes at an earlier and more primitive level of representation, which stores information about elementary attributes of the visual world, such as the orientation, color, motion, and texture of visual patterns . The function of this latter form of visual memory is not known but it might store information across fairly short time spans to help building permanent object representations. 2.2 Visual Representation in Episodic and Semantic Memory Visual recognition goes beyond the recognition of classes of objects. The picture in the morning paper is not just a sidewalk café, it is the Deux Magots in Paris, and the person in the front row is not just a female figure, it is the movie star Catherine Deneuve. 1 ..."
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"... Visual Processing Areas of the Brain Are Recruited in Memory Tasks Studies of memory processes in the human brain with modern brain imaging technology such as positron emission tomography (PET) and functional magnetic resonance tomography (fMRI) have shown that there is no special region of the brain where memories are stored. Memory involves widely distributed networks and all major regions of the cerebral cortex have been implicated in the various forms of memory. Since visual memory is a form of representation, a code rather than a system, one would expect it to share processing space with several memory systems, in addition to regions of the occipital lobe that are specific for the processing of visual signals. Memory researchers now generally agree that memories may involve many of the neural ensembles that were involved in the processing of the information in the first place. In vision a close link between perception and memory is illustrated by the observation that certain forms of perceptual deficits due to local brain lesions appear to affect memory as well. For example, persons who lose their ability to see colors owing to bilateral lesions of a region of the occipital lobe known as V4 usually also lose their ability to remember or imagine colors. The current debate on the neural mechanisms of visual memory does not consider whether sensory processing areas are recruited in memory, but how far down the processing hierarchy recruitment extends. Some brain imaging studies claim that the primary visual cortex (region V1), i.e., the very earliest level of sensory analysis receiving direct input from the eye, is activated in visual imagery tasks, but other studies do not find this activity . A logical argument may be directed against the involvement of early visual processing areas and a unification of visual perception and memory processes: Since memory images are normally much less vivid and detailed than perceptual images, and memory is rarely confused with perception, they must activate at least partly different neural circuits. The precise relationship between visual perception and visual memory is a major task for future research. 1 ..."
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"... Dissociation Between Visual Memory and Other Forms of Memory Lesions of the brain which disturb semantic and episodic memory may leave the perceptual recognition process intact. The patient's perception of the world is normal but he or she does not remember seeing these objects or persons before. Recognition memory may be demonstrated though perceptual priming (see Priming, Cognitive Psychology of ): If the patient is shown a drawing of an object and at a later time is shown the same drawing again, there is a gain in the time required to identify and name drawings that were previously seen compared with novel drawings, and the gain is comparable for amnesic and normal subjects. If, on the other hand, the link between visual memory representations and on-line perception is disrupted, amodal (verbal) episodic and semantic memory may be intact but the person can no longer recognize what he or she sees. In this condition of visual agnosia there may be nothing wrong with perceptual process per se , the person navigates safely in the geographic environment and may even copy diagrams and drawings, but the information which comes from vision is meaningless. 3 ..."
Reference 2
Reference works Chapter
Visual Memory, Psychology of
Magnussen S.
International Encyclopedia of the Social & Behavioral Sciences , 2015 pp 175-180
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"... Abstract When you open your eyes, your visual world immediately makes sense. This is achieved by some process by which online visual signals are matched to stored visual representations, and attest to the extraordinary capacity of visual memory. Information that enters the brain through the eyes is stored and remembered in terms of visual representations – in the form of images and sequences of images – or recoded and stored by the brain in terms of verbal or categorical representations. This multiple-coding principle of visual memory is part of the explanation why long-term visual memory generally outperforms other forms of memory. Visual memory recruits many of the brain areas that are involved in online perception, suggesting that the processes of visual perception and visual memory are closely interwoven. ..."
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"... Looking Ahead One of the major advances of modern cognitive science is the idea that the human mind is functionally organized in terms of multiple independent processing systems, each system devoted to a particular cognitive task. In vision research, the idea of parallel, specialized processing systems was quickly accepted following the pioneering studies of the Nobel laureates David Hubel and Torstein Wiesel (1959) , which showed that there were specialized neurons – in cognitive research termed channels – for processing features of the visual stimulus, such as color, orientation, size, and motion. The idea of modular organization of memory has had a slower progress. The current concept of visual memory identifies several memory systems as detailed above, and the distinctions between implicit and explicit memory systems, and the multiple-component working memory model, have been very successful in organizing the vast cognitive research literature. However, current neuroscience does not provide evidence for such a modular organization of memory, at least not if modules are defined in terms of localized brain processes. In the case of visual memory, an alternative view would be a model of memory that parallels the visual perceptual processing strategy of the brain, with the low- to higher-order specialization of the processing of visual features, objects, and scenes, and where different sensory areas are recruited depending upon the specific memory task. Modern research confirms that visual memory is superior to other forms of memory, being able to store vast amounts of information in terms of pictures or natural scenes. Visual memory, in the general definition of memory for information transmitted through the visual system, partly depends on information stored in terms of visual representations, and partly on information stored in terms of verbal or categorical representations. The extremely good retention of visual information of pictures and geographical scenes is likely to be the result of the multiple-systems operation of visual memory. It is the task of future research to specify the relative contributions of the different memory systems to the short-term and long-term visual memory performance, and to decide if the concept of memory systems is indeed a fruitful one. ..."
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"... The Visual–Spatial Sketchpad The support system referred to as the visual–spatial sketchpad is not a purely visual processing mechanism, but thought to combine information from visual, tactile, and haptic sensory channels. To a first approximation the visual–spatial sketchpad can be compared with the phenomenon of visual imagery. Visual imagery is the ability to produce ‘inner’ images of previously seen persons, objects, and geographical scenes, and to produce images of scenes that are simply imagined. Visual mental imagery tasks require subjects to retrieve information from long-term memory or to maintain visual information that has recently been viewed, and to perform cognitive operations on, or make judgments about, this information. The purely visual nature of visual imagery is supported by experiments showing that cognitive operations on visual mental images are governed by the same laws as similar operations performed on online visual images, and that visual imagery recruits many of the brain regions involved in online perception, even perhaps including some of the earliest brain regions in the visual process. This process is quite similar to the task of the visual–spatial sketchpad, and there is evidence that visual memory and imagery activate a number of common brain regions . However, whereas visual imagery is conceived as a conscious process of image generation, maintenance in visual working memory is not conceived as a conscious process in the same sense. Differences between visual imagery and the visual–spatial sketchpad are also suggested by the finding that visual imagery is disrupted by task-irrelevant visual noise whereas maintenance in visual working memory is not disrupted by visual noise . Thus, despite similarities, visual imagery and the visual–spatial sketchpad are not identical. 2 ..."
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"... Visual Processing Areas of the Brain Are Recruited in Memory Tasks Modern brain imaging techniques such as functional magnetic resonance imaging that allow fairly local and precise brain activity patterns to be mapped during the execution of cognitive tasks, would appear to offer a unique possibility of isolating the visual versus verbal components of working memory. But isolation of specialized memory systems is not a simple and straightforward procedure, both because cognitive tasks activate many brain systems concerned with perception, attention, and memory, and because most neural networks in the brain probably perform many processing tasks in parallel. Even if the performance on a specific visual memory task is not assisted by verbal memory, the simple fact that we identify a recognizable pattern that can be verbally classified and later remembered implies activation of verbal memory processes. Imaging studies have demonstrated distinct areas localized to the occipital and temporal lobes of the brain, specialized for processing particular classes of stimuli such as objects, scenes, and human faces . These regions are activated in visual memory tasks with these classes of stimuli but not in verbal memory tasks, suggesting that at least certain kinds of information is represented as visual codes. Otherwise, imaging of memory processes in the human brain has shown that there are no regions specialized for storing or maintaining memories . Memory involves widely distributed networks and all major regions of the cerebral cortex have been implicated in the various forms of memory. Since visual memory is a form of representation, a code rather than a system, one would expect it to share processing space with other cognitive memory systems, in addition to activation of the regions that are specific for the processing of visual information. Memory researchers generally agree that memories may involve many of the neural ensembles that were involved in the processing of the information in the first place, what is debated is how far down the processing hierarchy recruitment extends. Some brain imaging studies claim that the primary visual cortex (area V1), i.e., the very earliest level of sensory analysis receiving direct input from the eye, is activated in visual memory tasks . The role of these early regions in short-term and long-term visual memory is a challenge for future research. 3 ..."
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"... Some brain imaging studies claim that the primary visual cortex (area V1), i.e., the very earliest level of sensory analysis receiving direct input from the eye, is activated in visual memory tasks . The role of these early regions in short-term and long-term visual memory is a challenge for future research. They may be activated in visual recognition and delayed discrimination tasks, but it is less likely that they are activated in memory tasks involving visual imagery. Since memory images are normally much less vivid and detailed than perceptual images, and memory is rarely confused with perception, they must activate at least partly different neural circuits . 3 ..."
Reference 3
Book Chapter
Introduction to Emotion, Electroencephalography, and Speech Processing
Priyanka A. Abhang, Bharti W. Gawali, Suresh C. Mehrotra
Introduction to EEG- and Speech-Based Emotion Recognition , 2016 pp 1-17
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"... Other functions include help in formation of long-term memories and processing new information formation of visual and verbal memories interpretation of smells and sounds. 1.3.4 The Occipital Lobe The occipital lobe is located in the back portion of the brain behind the parietal and temporal lobes, and is primarily responsible for processing visual information. The occipital lobe contains the brain's visual processing system: it processes images from our eyes and links that information with images stored in memory. The occipital lobe, the smallest of the four lobes, is located near the posterior region of the cerebral cortex, near the back of the skull. It is the primary visual processing center of the brain; other functions include 9,10 visual-spatial processing movement and color recognition. 1 ..."
Reference 4
Book series Chapter
Mental Models and the Mind
Markus Knauff
Advances in Psychology , 2006 pp 127-152
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"... Results from neuroimaging With the development of new brain imaging methods the debate shifted from the behavioral findings towards the question of how reasoning and mental imagery is biologically realized in the human brain. Broadly speaking, the occipital lobe processes visual information. However, it is not only responsible for visual perception, but also contains association areas and appears to help in the visual recognition of objects and shapes. The occipital cortex can be divided into the primary visual cortex, also referred to as striate cortex or, functionally as V1, and to the visual association areas, also called the extrastriate cortex, or V2, V3, V4. The primary visual cortex receives visual input from the retina and is topographically organized, meaning that neighboring neurons have receptive fields in neighboring parts of the visual field. According to the cytoarchitectonic map of Brodmann (1909) , this region is called Brodmann’s area (BA) 17. The visual cortices have been frequently related to visual mental imagery. For instance, patients who are blind in one side of the visual field are also unaware of objects on that side when imagining a visual scene. If the patient turns the mental image around so that they had to “look” at the image from the opposite direction, they reported objects on the other side and ignored those which they had previously reported “seeing” . The strictest form of imagery theories has been elaborated on in the influential book by Kosslyn (1994) . In this book, Kosslyn claims that during mental imagery the geometrical information of remembered objects and scenes are processed in the primary visual cortex. Consequently, one of the central research issues on imagery is whether the primary visual cortex and nearby cortical areas are activated by visual mental imagery. Indeed, this assumption is supported by a series of studies by Kosslyn and his colleagues, who found increased blood flow in BA 17 during mental imagery of letters and objects in different sizes . Moreover, if participants imagined a letter, the larger letters activated a larger region of V1 while the smaller letters activated a smaller region . 1 ..."
Reference 5
Reference works Chapter
Short-Term Memory
Giuseppe Vallar
Encyclopedia of the Human Brain , 2002 pp 367-381
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"... When normal subjects are engaged in tasks involving short-term memory for spatial location, the activated areas include the occipital extrastriate (BA 19), posterior–inferior parietal (BA 40), dorsolateral premotor (BA 6), and prefrontal cortices. Short-term recognition memory for visual patterns (e.g., faces and designs) is associated with activation in a more ventral network, including the occipital and temporal (BA 37) regions, the posterior–inferior parietal region (BA 40), and the prefrontal cortex. Within the prefrontal cortex (BAs 45, 46, 47, and 9), more dorsolateral areas have been associated with short-term memory for spatial location and more ventral areas with short-term memory for patterns. Activation has frequently been found to be bilateral, but there is evidence suggesting more sustained activity in the right hemisphere when the task assesses recognition memory for spatial location and in the left hemisphere when the task probes recognition memory for visual patterns. These nonoverlapping patterns of activation indicate an association between the dorsal visual stream and short-term memory for spatial locations and between the ventral visual stream and recognition memory for visual patterns. These findings also suggest the existence of some hemispheric asymmetry, with right-sided areas being more concerned with the spatial (location) aspects of short-term retention and left-sided areas with the visual (pattern recognition) aspects. The relative contribution of different cerebral regions of the two sides of the brain may also be related to the format of the cerebral representation involved. For instance, a left lateralization for visual object working memory may reflect a more symbolic or verbal encoding and a right-sided lateralization a more image-based encoding. Finally, the different cerebral areas participating in the network may provide distinct contributions to the short-term retention process. The occipital and temporal regions may participate in perceptual analysis, the posterior parietal cortex in computing the coordinates of the stimulus, and the premotor and prefrontal cortices in the retention process (storage and rehearsal) proper. 1 ..."
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"... These nonoverlapping patterns of activation indicate an association between the dorsal visual stream and short-term memory for spatial locations and between the ventral visual stream and recognition memory for visual patterns. These findings also suggest the existence of some hemispheric asymmetry, with right-sided areas being more concerned with the spatial (location) aspects of short-term retention and left-sided areas with the visual (pattern recognition) aspects. The relative contribution of different cerebral regions of the two sides of the brain may also be related to the format of the cerebral representation involved. For instance, a left lateralization for visual object working memory may reflect a more symbolic or verbal encoding and a right-sided lateralization a more image-based encoding. Finally, the different cerebral areas participating in the network may provide distinct contributions to the short-term retention process. The occipital and temporal regions may participate in perceptual analysis, the posterior parietal cortex in computing the coordinates of the stimulus, and the premotor and prefrontal cortices in the retention process (storage and rehearsal) proper. 1 ..."
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"... A second type of impairment concerns the recognition of more than one visual stimulus at a time (defective simultaneous form perception): Patients who are able to identify single meaningful forms visually (letters, numbers, and geometric figures) are disproportionately impaired if two stimuli are presented, misidentifying one of them. In summary, lesion studies in brain-damaged patients provide support for the distinction between short-term memory for spatial locations and for visual patterns, the former being more closely associated with right hemisphere damage and the latter with left hemisphere damage. The lateralization of visuospatial short-term memory systems appears less pronounced than that of phonological memory. III.B.2 Measurement of Regional Cerebral Activity in Normal Subjects Neuroimaging activation studies in humans support and further qualify the distinction between primarily spatial (location) and visual (recognition) short-term memory components. The anatomical differences between them concern both the relevant cerebral areas and their prevailing lateralization. When normal subjects are engaged in tasks involving short-term memory for spatial location, the activated areas include the occipital extrastriate (BA 19), posterior–inferior parietal (BA 40), dorsolateral premotor (BA 6), and prefrontal cortices. Short-term recognition memory for visual patterns (e.g., faces and designs) is associated with activation in a more ventral network, including the occipital and temporal (BA 37) regions, the posterior–inferior parietal region (BA 40), and the prefrontal cortex. Within the prefrontal cortex (BAs 45, 46, 47, and 9), more dorsolateral areas have been associated with short-term memory for spatial location and more ventral areas with short-term memory for patterns. Activation has frequently been found to be bilateral, but there is evidence suggesting more sustained activity in the right hemisphere when the task assesses recognition memory for spatial location and in the left hemisphere when the task probes recognition memory for visual patterns. 1 ..."
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"... Impairments of Short-Term Memory for Visual Patterns The short-term visual recognition of unfamiliar faces, objects, voices, and colors may be impaired following brain damage. These deficits may be associated with defective short-term memory for spatial locations. The disorder of patients with defective visual imagery (e.g., as assessed by tasks requiring color or size comparisons) may also be interpreted in terms of a defective visual short-term memory store. A deficit of visual short-term memory may disrupt long-term learning of unfamiliar nonverbal material, as assessed by recognition memory for unfamiliar faces and objects. This extends to the visuospatial domain the conclusion that long-term acquisition requires short-term storage. 3 ..."
Reference 6
Reference works Chapter
Short-term memory
Vallar G.
Reference Module in Neuroscience and Biobehavioral Psychology , 2017
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"... Damage to the premotor, and prefrontal dorsomedial regions of the right hemisphere may specifically disrupt the rehearsal of spatial information, causing disproportionate short-term forgetting in the range of seconds . Damage to the right hemisphere may also affect STM for unfamiliar faces . Conversely, PhSTM is not impaired by lesions in the right hemisphere. Some deficits of visual STM are associated with damage to the posterior (parieto-occipital) regions of the left hemisphere. One such impairment concerns the immediate retention of sequences of visual stimuli, such as straight or curved lines . This deficit may occur in the presence of a normal auditory-verbal span. In sum, lesion studies in brain-damaged patients provide support to the distinction between STM for spatial locations and for visual patterns, the former being more closely associated with right hemisphere damage, the latter with left hemisphere damage. The hemispheric lateralization of neural networks concerned with visuo-spatial STM, particularly for the visual component, is less pronounced than that of the networks supporting PhSTM. The anatomical differences between primarily spatial (location, “where”) and visual (recognition “what”) STM components concern both the relevant cerebral areas and their prevailing lateralization. When healthy participants are engaged in tasks involving STM for spatial location the activated areas include the occipital extra-striate (BA 19), the posterior parietal, dorsolateral premotor (BA 6) and prefrontal cortices. Short-term recognition memory for visual patterns (eg, faces, designs) is associated with activation in a more ventral network including the occipital and temporal (BA 37) regions, the posterior-inferior parietal region , and the prefrontal cortex. Within the prefrontal cortex (BA 45, 46, 47, 8, 9), more dorsolateral areas have been associated with STM for spatial location, more ventral areas with STM for patterns. 1 ..."
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"... Activation has been frequently found to be bilateral, but there is evidence suggesting more sustained activity in the right hemisphere when the task assesses recognition memory for spatial location, in the left hemisphere when the task probes recognition memory for visual patterns. These non-overlapping patterns of activation indicate an association between the “dorsal visual stream” and STM for spatial locations, and between the “ventral visual stream” and recognition STM for visual patterns. These findings also suggest the existence of some hemispheric asymmetry, with right-sided areas being more concerned with the spatial (location) aspects of short-term retention, left-sided areas with the visual (pattern recognition) aspects. The relative contribution of different cerebral regions of the two sides of the brain may also be related to the format of the cerebral representation involved. For instance, a left lateralization for visual object STM may reflect a more symbolic or verbal encoding, a right-sided lateralization a more image-based and spatial encoding. Finally, the different cerebral areas participating in the network may provide distinct contributions to the short-term retention process. The occipital and temporal regions may mainly participate in perceptual analysis, the PPC in computing the coordinates of the stimulus and in providing the capacity for STS, the premotor and prefrontal cortices in the rehearsal and retention processes . 1 ..."
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"... Visual and Spatial STM STM for spatial locations, as assessed by tasks requiring the reproduction of sequences of positions in near extra-personal space, is disrupted by damage to the posterior (parieto-occipital) regions of both the left and the right hemisphere, but the role of right hemisphere damage appears to be more relevant . These early suggestions have been confirmed and specified by whole brain voxel-based morphometry and tract-wise lesion deficits analyses: bilateral occipital damage (middle occipital gyrus), and damage to the right IPL and the TPJ, with disconnection of the right parieto-temporal segment of arcuate fasciculus, are associated with low spatial memory span . Studies in individual right-brain-damaged patients suggest that a network including the dorsomedial posterior parietal cortex (BA 7), and the dorsal premotor cortex (BA 6) is involved in STM for spatial locations (assessed, for instance, by Corsi's test, see Fig. 11 A), with verbal and visual STM being spared . Damage to the premotor, and prefrontal dorsomedial regions of the right hemisphere may specifically disrupt the rehearsal of spatial information, causing disproportionate short-term forgetting in the range of seconds . Damage to the right hemisphere may also affect STM for unfamiliar faces . Conversely, PhSTM is not impaired by lesions in the right hemisphere. Some deficits of visual STM are associated with damage to the posterior (parieto-occipital) regions of the left hemisphere. One such impairment concerns the immediate retention of sequences of visual stimuli, such as straight or curved lines . This deficit may occur in the presence of a normal auditory-verbal span. In sum, lesion studies in brain-damaged patients provide support to the distinction between STM for spatial locations and for visual patterns, the former being more closely associated with right hemisphere damage, the latter with left hemisphere damage. 1 ..."
Reference 7
Review article
Neural representation of visual objects: Encoding and top-down activation
Miyashita Y., Hayashi T.
Current Opinion in Neurobiology , 2000 pp 187-194
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"... The inferior temporal (IT) cortex — the final stage of the ventral processing stream devoted to object vision — has long been assumed to serve as the storehouse of visual long-term memory [2,4,5] . Using single-unit recordings in monkeys performing visual memory tasks, the neuronal correlates of long-term memory have been identified in the anterior ventral part of the IT cortex [5–7] . Specifically, a class of neurons (called pair-coding neurons) have been found to exhibit significantly correlated visual responses to arbitrarily assigned picture pairs in a visual stimulus–stimulus association task [8,9] , demonstrating that IT neurons can establish new linkage between different stimuli that have meaningful connections. 1 ..."
Reference 8
Reference works Chapter
Reward neurophysiology and primate cerebral cortex
Kobayashi S.
Encyclopedia of Neuroscience , 2009 pp 325-333
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"... Temporal Cortex The inferior temporal (IT) cortex plays a critically important role for the visual recognition of objects. The visual recognition system in the IT cortex is distributed in multiple areas, including area TE and the rhinal cortex. Area TE is a unimodal visual-association area located at the final stage of the ventral visual pathway. The rhinal cortex, which consists of the perirhinal and entorhinal cortices, is a limbic polymodal association area located in the medial temporal lobe. Primate research has revealed that (1) lesions in these areas produce deficits in visual recognition memory, (2) TE neurons selectively respond to various complex features of objects, and (3) the perirhinal cortex is involved in the retrieval of visual long-term memory. In addition to the functions of visual recognition and memory, IT cortex plays an important role in associating visual stimuli with reward outcome. Anatomically, area TE and the rhinal cortex are mutually interconnected. The perirhinal cortex has strong connections with reward-related sites, including the amygdala, OFC, ventral striatum, and midbrain dopamine neurons. Lesions in the IT cortex cause behavioral changes that depend on reward schedule. In one study, monkeys learned a task in which visual cues indicated the number of successful trials (one, two, or three) required to receive a reward. Monkeys performed each trial differently depending on the reward schedule, but lesioning or suppressing the expression of dopamine D2 receptors in the perirhinal cortex abolished the reward-schedule-dependent behavior. Neurons in the IT cortex show activity related to reward. When monkeys perform a go/no-go task in which each visual cue indicates a required action (release or keep pressing a lever) as well as reward availability, approximately one-third of perirhinal neurons and one-fifth of TE neurons show sensitivity to reward availability. 1 ..."
Reference 9
Book Chapter
Visual Cortices Participating in Visual Memory and Visual Imagery
PER E. ROLAND, JEAN DECETY
Functional Organisation of the Human Visual Cortex , 1993 pp 373-385
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"... Working Memories, Long Term Storage Sites and Visual Imagery Although there were some differences in stimuli and the operations required on the stimuli in these three PET studies there were also some strong similarities. In the route finding task, the visual recall and the preparation for reaching task, the subjects all imagined a visual pattern. In the route finding task the pattern was a full visual field scene, in the other two tasks the stimuli to be imagined were 33 by 33 degrees visual stimuli. These are stimuli which stimulate a large part of the visual field. In this sense all material that was imagined contained spatial properties, which demanded a change in the gaze to sample all relevant visual information. On the other hand, during the route finding task the subjects had to perform detailed operations on the visual scenes recalled from memory. This task resulted in an activation of many remote visual association areas ( Table 1 ). With the exception of the supramarginal gyrus, these areas were also activated in the visual learning task. Furthermore, the areas activated by visual learning located in the posterior precuneus, posterior superior parietal lobule, posterior intraparietal sulcus, and angular gyrus have also been activated in visual discrimination of shape . Therefore, one can state that these areas in the posterior precuneus, posterior superior parietal lobule, posterior intraparietal sulcus, and angular gyrus are visual association areas . Of these areas the posterior precuneus, the posterior superior parietal lobule, and the angular gyrus were activated when subjects recalled patterns and scenes from visual memories. These areas were also activated when the subjects learned visual patterns. It is therefore possible that these remote areas are part of the storage sites for large field visual patterns. The posterior inferior temporal cortex was activated in the route finding task, and the visual learning task and in the pattern recall task . It is possible that this is also a remote visual association area. However, at present there are no further experimental results which can clarify its role as storage site for visual information. In none of these three PET studies have we been able to detect consistent changes in rCBF more rostrally in the inferior temporal cortex. This might well be because we have used large field stimuli. 1 ..."
Reference 10
Reference works Chapter
Declarative Memory
Brianne Bettcher
Encyclopedia of the Neurological Sciences , 2025 pp 404-409
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"... Medial Temporal Lobes Episodic memory is a complex set of cognitive operations that can be influenced by attention/concentration and executive functions, in addition to memory consolidation processes. As such, episodic memory is mediated by multiple neurological pathways and systems. Extensive research with primate and neurological patients, however, has demonstrated that the key regions underlying one's ability to learn and consolidate information about events that occurred in the recent past are in the medial temporal lobes. The primary structure linked to episodic memory learning is the hippocampus, a small structure shaped like a seahorse tucked deep in the medial portion of each temporal lobe . Patients with bilateral lesions in the hippocampus typically present with dense amnesia that involves difficulties recalling information in the recent past (known as retrograde amnesia) as well as an inability to learn new information (known as anterograde amnesia). Old semantic information and basic perceptual and intellectual functioning may be grossly unaffected, although further probing of these areas can reveal additional deficits. More extensive experiments have shown that the hippocampus is just one part of an extensive information-processing network that contributes to memory performance. Information being processed in all parts of the neocortex projects to the amygdala, parahippocampal gyrus, and perirhinal cortex before being transmitted to both anterior and posterior regions of the entorhinal cortex. The entorhinal cortex serves as the primary entrance to the hippocampus. The hippocampus has been subdivided into key subregions that move information in a prototypical manner: Information projects first to the dentate gyrus via the perforant path, and then to the CA3 and CA1 regions. Information leaving the hippocampus enters the subiculum and entorhinal cortex before being projected back to the cortex. However, information leaving the CA1 and subiculum can also bypass the entorhinal cortex and directly connect with other cortical regions. Projections to the cortex are widely distributed, with multiple cortical regions contributing to a memory trace. 1 ..."
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"... Importantly, memories typically contain both episodic and semantic information, allowing for a more vivid representation of the memory. Assessment of Episodic Memory Verbal episodic memory can be assessed in a variety of ways at the bedside. The most common approach to assessment involves the administration of either a list-learning task or paragraph recall. List-learning tasks entail auditory presentation of a list of words over a series of several trials (verbal learning); patients are typically required to recall as many words as they can remember after each trial, and they are subsequently tested again after short and long delay periods (verbal recall). In some verbal memory paradigms, participants are provided categorical cues to see if leveraging semantic information/grouping facilitates retrieval (referred to as “cued recall”). Finally, patients are often administered a forced-choice recognition trial (verbal recognition), which can be helpful in differentiating problems with memory consolidation vs problems due to memory retrieval. With the latter, patients may perform poorly on delayed recall trials, but they typically improve with recognition memory formats. Another type of verbal episodic memory test is story or paragraph recall. This entails the administration of a brief story, and patients are required to recall as many details of the story as they can, both immediately after presentation of the story and after a delay period. Visual episodic memory is typically assessed using nonverbal analogs of the aforementioned measures, and often includes visual learning, recall, and recognition of geometric designs or faces. Neural Substrates of Episodic Memory Medial Temporal Lobes Episodic memory is a complex set of cognitive operations that can be influenced by attention/concentration and executive functions, in addition to memory consolidation processes. As such, episodic memory is mediated by multiple neurological pathways and systems. Extensive research with primate and neurological patients, however, has demonstrated that the key regions underlying one's ability to learn and consolidate information about events that occurred in the recent past are in the medial temporal lobes. The primary structure linked to episodic memory learning is the hippocampus, a small structure shaped like a seahorse tucked deep in the medial portion of each temporal lobe . 1 ..."
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"... Although it was previously thought that the medial temporal lobes played a role only in early encoding and development of episodic memories, there has been additional evidence suggesting a more complicated and central role for the hippocampus and medial temporal lobe structures in long-term recall of episodic information. Specifically, numerous functional neuroimaging studies have demonstrated that hippocampal activation is associated with detailed, vivid episodic memories, regardless of the memories' age, and may be involved in reconstructing or developing additional “traces” of the original memory . Thus, although the hippocampus may not eventually be necessary for the gist of an episodic memory, retrieving and reconstructing details and explicit contextual information may be still be dependent on these structures, even for recall of very old memories. Frontal and Parietal Lobes Accumulating research also underscores a critical role for broader brain regions involved in the default mode network (DMN) and the frontal-parietal network in episodic memory , particularly dorsomedial and ventral lateral prefrontal regions. Neuroimaging studies show that frontal systems are important for the spontaneous use of strategies during encoding of new information (e.g., organizing and grouping information), monitoring search processes and temporal order when recalling information, utilizing self-referential processing when retrieving event details, and identifying the source of episodic memories. The latter process is often referred to as “source memory,” and refers to specific recall for the source and context of a fact or message (e.g., who said something and when this occurred, rather than what was said). Although episodic memory has traditionally been conceptualized as a medial temporal- and frontal lobe-driven process, the advent of functional neuroimaging has shown that the parietal lobes play a key role in these processes. Posterior and lateral parietal regions, particularly the posterior cingulate, precuneus, superior parietal lobule, and retrosplenial gyrus, have received increasing recognition for their role in harnessing attention and working memory processes during encoding and recall of episodic memories, as well as their roles in the retrieval of spatial aspects of episodic memory. 1 ..."
Reference 11
Review article
Single unit approaches to human vision and memory
Kreiman G.
Current Opinion in Neurobiology , 2007 pp 471-475
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"... The representation of visual memories Several pieces of evidence suggest that the highly selective responses by MTL neurons should not be exclusively attributed to visual recognition or visual perception. These responses could well reflect a role of the MTL in memory trace formation, memory consolidation and information retrieval: (i) The MTL receives information from different modalities [ 8 ]; (ii) Subjects with MTL lesions or excisions show profound deficits in the formation and consolidation of novel declarative memories. Yet, the visual recognition capabilities seem to remain largely intact [ 7–9 ]; (iii) The latencies of human MTL neurons are rather long for immediate visual object recognition [ 26 ]; (iv) Assuming parsimony and extrapolating from animal studies, extensive evidence from molecular and physiological experiments strongly suggest a prominent role for the MTL in memory formation and consolidation (e.g. [ 8,9 ]), (v) Electrical stimulation in the human MTL can disrupt memory formation [ 43 ]. There is a close link between memory and recognition [ 25,26,44 ]. Most models of visual object recognition postulate a comparison between the incoming input and existing templates or centers from radial basis function units (e.g. [ 25–27,44 ]). Consistent with this notion, recordings in the human MTL suggest that these neurons may play an important role in memory processes. In a word-pair association task, the activity of hippocampus neurons during the association/encoding phase could predict whether the subjects would remember those word pairs [ 45 ]. In another study, neurons in the human MTL were selectively activated when subjects mentally recalled information about an image that had been visually presented several seconds before [ 46 ]. After seeing images presented on a monitor, the subjects were instructed to mentally recall one image or the other. Several MTL neurons modulated their activity in a selective fashion during visual recall ([ 46 ] see also [ 47 ]). An important first step in the formation of new memories may be the distinction between familiar and novel information. 1 ..."
Reference 12
Book Chapter
Hemispheric Organization of Visual Memory: Analyzing Visual Working Memory With Brain Measures
Gratton G., Shin E., Fabiani M.
Mechanisms of Sensory Working Memory , 2015 pp 75-88
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"... Results and Discussion Demonstrating the Hemispheric Organization of Visual Memories Our initial demonstration that visual memories are hemispherically organized was obtained using a recognition paradigm . We presented subjects with lists of unique, novel, line-based, visual stimuli flashed to the left or right of a fixation cross. Subjects were given a superficial orienting task (indicating whether the stimuli were symmetrical along the vertical or horizontal axis). In three different behavioral studies, the same stimuli were then presented in another location of the same hemifield (varying in distance depending on the experiment) or of the opposite hemifield, intermixed with an equal number of new stimuli, and subjects were asked to provide an old/new judgment. In all the experiments, there was an accuracy advantage when the stimuli were re-presented to the same hemifield with respect to when they were re-presented to the opposite hemifield (see Figure 2 ). This advantage persisted even when the physical distance between the first and second presentations of the stimuli were matched for the within- and across-hemifield conditions. In a fourth experiment, we presented the test stimuli at the center (fixation), recorded ERPs, and computed ERL waveforms. The waveforms (also shown in Figure 2 ) indicated the presence of systematic ERL effects, maximum over temporal scalp locations, consistent with the idea that visual memories are indeed hemispherically organized. Interestingly, when subjects were asked to indicate whether each stimulus had been presented initially to the left or right of fixation, their performance was at chance. This suggests that subjects did not use a simple mnemonic strategy associating a stimulus with a side of presentation and that they were not aware of where the stimuli were originally presented. Fabiani, Stadler, and Wessels (2000) used a similar paradigm to investigate whether, in the Deese-Roediger-McDermott (DRM) paradigm , real and illusory memories could be distinguished at retrieval on the basis of their associated brain activity. 2 ..."
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"... In addition to ERPs, we also recorded EROS from occipital areas in this paradigm . An advantage of EROS with respect of ERPs is that signals are much more localized. As a consequence, the responses of individual brain regions can be analyzed separately. This means that it is possible to isolate the activity elicited by test stimuli from brain regions ipsilateral and contralateral to the encoding side. It is also possible to compare these responses with those obtained when the test stimulus was new (i.e., it was not part of the memory set). These data are presented in Figure 4 . They indicate that early (80-ms latency) responses in medial occipital cortex were visible in both hemispheres for new items and in the hemisphere ipsilateral to side of encoding for items that were part of the memory set. In other words, responses are reduced in the region of the brain that had just been exposed to the same stimulus. Further, analyses at longer latencies and in different brain regions revealed additional responses, including enhanced activity for “old” items. This suggests that adaptation may not be the only process associated with sensory working memory: template matching or recognition may also occur. Permanence versus Top-Down Creation of Expectations: Masking Studies Taken together, these results indicate that the lateralized presentation of visual stimuli leaves “traces” in the hemisphere contralateral to the encoding side. This gives rise to an “adaptation” effect by which subsequent presentations of the same stimulus to the same hemisphere require less processing (and are associated with reduced brain activity). This adaptation phenomenon may reflect the permanence of latent activation of the neural circuitry in the aftermath of the initial processing. Alternatively, it may reflect top-down activation of the sensory circuitry, exerted by control processing areas higher up in the information processing hierarchy, and in preparation for the upcoming test stimulus. An additional question is the role of adaptation in influencing the subjects’ behavior. 2 ..."
Reference 13
Book Chapter
Visual Thinking Processes
Colin Ware
Information Visualization , 2013 pp 375-423
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"... Memory and Attention As a first approximation, there are three types of memory: iconic, working, and long-term (see Figure 11.2 ). There may also be a fourth, intermediate store that determines which information from working memory finds its way into long-term memory. Iconic memory is a very short-term image store, holding what is on the retina until it is replaced by something else or until several hundred milliseconds have passed . This is image-related information, lacking semantic content. Visual working memory holds the visual objects of immediate attention. The contents of working memory can be drawn from either long-term memory (in the case of mental images) or input from the eye, but most of the time information in working memory is a combination of external visual information made meaningful through the experiences stored in long-term memory. Long-term memory is the information that we retain from everyday experience, perhaps for a lifetime, but it should not be considered as separate from working memory. Instead, working memory can be better conceived of as information activated within long-term memory. Of the three different stores, working memory capacities and limitations are most critical to the visual thinking process. Working Memories There are separate working memory subsystems for processing auditory and visual information, as well as subsystems for body movements and verbal output . There may be additional working memory stores for sequences of cognitive instructions and for motor control of the body. Kieras and Meyer (1997) , for example, proposed an amodal control memory containing the operations required to accomplish current goals and a general-purpose working memory containing other miscellaneous information. A similar control structure is called the central executive in Baddeley and Hitch's (1974) model. A more modern view is that there is no central processor; instead, different potential activation loops compete with a winner-take-all mechanism, causing only one to become active. This determines what we will do next . Visual thinking is only partly executed using the uniquely visual centers of the brain. 2 ..."
Reference 14
Book series Chapter
Scaling up visual attention and visual working memory to the real world
Brady T.F., Stormer V.S., Shafer-Skelton A., Williams J.R., Chapman A.F., Schill H.M.
Psychology of Learning and Motivation , 2019 pp 29-69
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"... Visual working memory 3.1 Introduction Visual working memory is a system used to actively store and manipulate visual information . This memory system is severely limited in capacity , and the capacity limits of the active storage system in particular are closely related to measures of intelligence and academic achievement , suggesting that active storage in visual working memory may be a core cognitive ability that underlies, and constrains, our ability to process information across domains . The vast majority of studies on visual working memory have focused on memory for simple stimuli like colored squares, oriented lines or novel shapes; these are all stimuli about which participants have minimal background knowledge or expectations. These simple, meaningless stimuli are assumed to best assess the core capacity of working memory because they have no semantic associations and are repeated from trial-to-trial, which minimizes participants' ability to use other memory systems, like episodic visual long-term memory . Episodic long-term memory is the process of forming memory traces and later retrieving them without continued active maintenance, and it can be used at any time scale (even with brief delays). Contributions from this system, which operates best with conceptually meaningful stimuli and when there is little interference from items repeating across trials , are thought to be minimal in working memory tasks that use simple, meaningless stimuli. However, while studies using such simplified stimuli have provided critical insights into the structure of the working memory system and the nature of its capacity, they also leave out many important aspects of visual memory in the real world. In particular, in the remaining part of the chapter we argue that (1) meaningfulness, knowledge, and familiarity play an important role in visual working memory and in shaping its capacity; (2) memory for scenes and surfaces is critical in the world, not just memory for objects; (3) even in the case of memory for objects, important regularities between objects often give rise to ensemble information, rather than just individual object representations. Many of these factors are rarely studied in the context of visual working memory, and when they are it is often with stimuli that—while having extremely strong external validity—are difficult to fully understand in terms of representations and processes . How does visual working memory function when these more realistic factors are present? 2 ..."
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"... That is, even for identical images, being able to recognize something as a meaningful “unit” (a face) rather than treating it as a set of meaningless mid-level features results in improved memory performance. In visual working memory, this results in improved “capacity,” and also a larger CDA, again suggesting a change in the capacity of the active storage system rather than the use of non-active forms of memory. Together, then, there is significant evidence that visual working memory is importantly different depending on the content of the memory. In particular, stimuli that form meaningful units, or even stimuli that have learned associations (e.g., color pairs), seem to allow for greater performance in visual working memory. 3.5 Expertise and visual working memory In addition to general knowledge and associations impacting visual working memory, it is often the case in the real world that we must engage working memory in complex tasks for which we have some particular level of expertise. How does visual working memory take into account such person-specific prior knowledge in a particular area? It is widely known that expertise and knowledge improve our ability to maintain information . For example, experts show an increased visual working memory capacity for images in their domain: expert car dealers have a greater capacity to remember cars compared to novices . Recent work has examined the impact of expertise in working memory in other more applied domains of expertise. For example, building on work studying expert radiologists which shows they have increased long-term recognition memory for medical images , we have recently been examining whether this expertise also impacts their ability to remember mammogram images over shorter, working memory delays . We have hypothesized that similar to the effects observed in long-term memory, there could be expertise-specific effects in working memory not because of the well-known benefits of chunking , but because of improvement that occurs because of existing memory for what variation exists for an image in an expert's domain (e.g., they know how mammograms might vary and so can encode diagnostic features). 2 ..."
Reference 15
Book Chapter
Thinking With Visualizations
Colin Ware
Information Visualization , 2021 pp 393-424
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"... Visual Working Memory Capacity Visual working memory holds three kinds of information. The first is a small amount of information from what has previously been observed. This consists of the shape, color, texture, and location of about three to five simple objects . The exact number depends on the task and the kind of pattern, and the amount of shape information is strictly limited to the very basic structure. The second kind of information is mental imagery that is imagined objects and their layouts in space , which is also is limited to a very small number of items. The third kind of information is the contents of a visual query. If you are looking for something specific you will be much less likely to notice changes in other visual information. Information in visual working memory is held only for 1 or 2 seconds. Most if the time it lasts only for a fraction of a second as it replaced by new information from the current fixation. Fig. 11.3 (a) illustrates the kinds of patterns used in a series of experiments by Vogel, Woodman, and Luck (2001) to study the capacity of visual working memory. In these experiments, one set of objects was shown for a fraction of a second (e.g., 0.4 second), followed by a blank of more than 0.5 second. After the blank, the same pattern was shown, but with one attribute of an object altered—for example, its color or shape. The results from this and a large number of similar studies have shown that about three objects can be retained without error, but these objects can have color, shape, and texture. If the same amount of color, shape, and texture information is distributed across more objects, memory declines for each of the attributes. Only quite simple shapes can be stored in this way. Each of the mushroom shapes shown in Fig. 11.3 (b) uses up two visual memory slots . Subjects do no better if the stem and the cap are combined than if they are separated. Intriguingly, Vogel et al. (2001) found that if colors were combined with concentric squares, as shown in Fig. 11.3 (c) , then six colors could be held in visual working memory, but if they were put in side-by-side squares, then only three colors could be retained. 2 ..."
Reference 16
Review article
Looking for the neural basis of memory
Kragel J.E., Voss J.L.
Trends in Cognitive Sciences , 2022 pp 53-65
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"... A clearer view of memory reinstatement Eye movements provide rich spatiotemporal information that can reveal the quality of memory processing. Studies of hippocampal function typically focus on questions of how spatial and temporal information is bound into memory representations [ 58–60 ]. Because vision is a primary form of exploration in primates [ 61 ], eye movements are well suited to these research questions because they translate continuous visual inputs into discrete sequences associated with specific spatial locations. Eye-movement behaviors thus provide a means of tracking the spatiotemporal information in memory during both encoding and retrieval. It is widely held that memory retrieval involves reinstatement of neural activity that is present during initial encoding. Indeed, functional neuroimaging studies have shown that hippocampal activity at encoding and retrieval predicts both item-specific and episode-specific reinstatement of individual memories [ 62–65 ]. However, experiments have not typically considered behavioral reinstatement, such as in patterns of eye movements, that likely accompanies neural reinstatement. Theories of visual memory propose that the sequence of eye movements becomes incorporated into memory during encoding, and memory recall involves reinstatement of the same sequence of eye movements [ 66 , 67 ]. Recent studies provide behavioral evidence that successful scene retrieval is marked by such reinstatement [ 35–37 ], making reinstatement of fixation sequences a behavioral measure of memory reinstatement. This raises a key interpretive challenge for previous studies of neural pattern reinstatement because neural reinstatement could have been secondary to behavioral reinstatement. This issue is exemplified in a recent study wherein subjects performed a memory task in which they imagined scenes from either long-term or short-term memory [ 68 ]. Simultaneous eye tracking and fMRI revealed reinstatement of neural activity and fixations when imagining visual content from both long-term and short-term memory. Further, neural reinstatement positively correlated with fixation reinstatement, indicating that eye movements may be functionally relevant in generating neural reactivation. 2 ..."
Reference 17
Book Chapter
Disorders of higher cortical visual function
Grant T. Liu, Nicholas J. Volpe, Steven L. Galetta
Neuro-Ophthalmology , 2010 pp 339-362
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"... Visual memory disturbances The ability to remember visual information requires storing then retrieving it. 184 Functional MRI studies suggest that extrastriate cortical regions used for visual perception are also initially utilized in visual memory tasks. 185 Subsequently, a network involving temporal lobe, hippocampal, and ventrolateral prefrontal cortex mediates human visual working memory, which is the process of retaining visual information for a brief period so that is available for immediate use. 186–189 Then visual information is stored using long-term memory systems. Clinical observations in brain damaged individuals support these notions. Ross 190 reported two patients with bilateral posterior temporal lobe infarctions and loss of visual recent memory. Tactile, verbal, and nonverbal auditory memory functions were normal, but they could not recognize faces. Attributing the visual memory deficit to a disconnection syndrome, he hypothesized the bilateral lesions disrupted tracts between primary visual cortex and structures important for memory, such as the medial temporal lobe. Other patients with similar bilateral temporal lobe lesions and prosopagnosia have been described, 8 , 9 suggesting recognition of faces and visual memory share similar mechanisms. Evidence for lateralization and the role of the right temporal lobe in visual memory is provided by studies in right temporal lobectomy patients, who exhibit defective recognition of visual material; 191 a patient with damage to the right frontotemporal region following middle cerebral artery aneurysm rupture who had defective memory of new visual objects and faces; 192 and posterior cerebral artery amobarbital tests, which suggest the right temporal lobe is important for remembering visual aspects of an object, while the left temporal lobe is more critical for recalling the object's verbal representation. 193 Other similar patients with impaired visual memory have been described following infarction of the right dorsomedial thalamic nucleus 194 and damage to the anterior commissure and right fornix, 195 structures also important in the formation and retrieval of visual information. 2 ..."
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"... 413 The visual deficits in Alzheimer's disease are usually attributed to neurofibrillary tangles in visual association areas 414–416 or striate cortex. 417 Levine et al. 418 described a patient with Alzheimer's, visual object agnosia, visual field constriction, and impaired contrast sensitivity. The postmortem examination revealed the density of tangles was highest in the occipitoparietal areas and lowest in the frontal lobes. A similar distribution of lesions was found in a group of Alzheimer's patients presenting with Balint syndrome. 419 Alzheimer's patients who are visually symptomatic are more likely to demonstrate tangles in the occipitoparietal regions than those who have normal visual function. 420 Pathologic findings in the primary visual pathways have also been found, 404 but like analogous clinical observations, the results are inconsistent. For instance, the density of retinal ganglion cells subserving the central 11 degrees of vision was reduced in patients with Alzheimer's disease as well as in age-matched control patients. 421 Treatment . A detailed overview of the various pharmacologic agents used in Alzheimer's disease is beyond the scope of this section, so the reader is referred to reviews on this topic. 369,422–427 However, some principles will be discussed here. In general, there is no cure and no method for halting disease progression, and these medications are only mildly effective, at best. Based upon notion that enhancing central cholinergic neurotransmission might improve the cognitive and behavioral aspects of Alzheimer's disease, cholinesterase inhibitors such as donepezil, rivastigmine, and galantamine can be used. 428 However, gastrointestinal side-effects such as nausea and diarrhea are common. Despite its proven efficacy, the use of another cholinesterase inhibitor, tacrine (tetrahydroaminoacridine) is limited because of the risk of hepatotoxicity. 3 ..."
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"... The visual disturbances tend to be higher cortical in nature. 363 , 377 In one study 378 of community based patients with Alzheimer's disease, approximately one-half had a visual object agnosia, while one-fifth had Balint syndrome. Prosopagnosia, visual hallucinations (see Chapter 12 ), defective visual motion perception, 379–381 abnormal form perception, 382 decreased visual attention, 383 poor performance on visuospatial tasks, 384 , 385 right-sided neglect, alexia without agraphia, poor visual memory, 386 and diminished curiosity of novel or unusual visual stimuli 387 may also occur. Because patients with Alzheimer's disease and higher cortical visual disturbances usually have normal visual acuity, relatively clear ocular media, and normal fundus appearance, many such patients have persistent visual complaints despite visits to several ophthalmologists and numerous changes in eyeglass prescriptions. In addition, patients with Alzheimer's disease may also have more elementary visual deficits involving the primary visual pathways. Deficits in visual acuity, 388 visual fields including hemianopic field loss, 377,389–391 contrast sensitivity, 392 stereoacuity, 393 , 394 and color vision 395 have all been observed. However, some of these results are only inconsistently observed, and some studies are hampered by limitations in patient testing. For instance some authors 396 , 397 were unable to demonstrate any abnormalities in primary visual function that were not also observed in age-matched controls. In addition, in one study 398 of patients with Alzheimer's disease who underwent computerized perimetry, many had nonspecific visual field constriction. However, the numbers of fixation losses and false-negative and -positive responses for each patient were very high, making any conclusions difficult. Diagnostic studies. The results of neuroradiologic studies, both anatomic and functional, tend to be nonspecific in patients with Alzheimer's disease. CT and MRI, although helpful in excluding a mass lesion, multiple infarcts, or normal pressure hydrocephalus, is usually either normal or reveals diffuse cortical atrophy. 3 ..."
Reference 18
Reference works Chapter
In Search of Engram Cells
Roy D.S., Tonegawa S.
Learning and Memory: A Comprehensive Reference , 2017 pp 637-658
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"... These pioneering studies led to a notion that at least some types of memory, in this case episodic memory, may be stored in a localized brain region. More recent work using single-unit recordings in humans reported that cells in the hippocampus and surrounding areas were reactivated only during free memory recall of a particular individual, landmark , or episode . Among early attempts to identify memory engrams in monkeys, one study recorded single-cell activity from the inferotemporal (IT) cortex during a visual delayed matching-to-sample task . Many cells responded to the colors of the stimuli, and notably, several cells responded differentially to color depending on whether or not attention circuitry was engaged, thus demonstrating their behaviorally relevant role. Fittingly, the authors demonstrated correlations of these neuronal activities to the encoding, retention, and retrieval of visual information. Later, Yasushi Miyashita (1988) revealed a neuronal correlate of visual long-term memory by studying how the anterior ventral temporal cortex represented stimulus–stimulus associations. By simultaneously recording from over 200 neurons as monkeys performed a visual memory task, single neurons that could respond conjointly to temporally related, but geometrically dissimilar stimuli were observed. That is, certain neurons displayed stimulus selectivity during the learning phase of the task, which then could become associated with unrelated stimuli in a different experience. These elegant studies demonstrated a neuronal correlate of associative visual memory. In a more recent series of experiments, using two-photon imaging in macaques to follow the remodeling of intracortical axons after retinal lesions over extended periods of time, it was found that lesions induced an almost immediate increase in the number of axonal boutons as well as axonal collaterals within the affected cortical region . Thus, presynaptic elements of cortical circuitry are also modified following experience-dependent changes. 2 ..."
Reference 19
Book Chapter
Neural and Behavioral Correlates of Auditory Short-Term and Recognition Memory
Poremba A.
Mechanisms of Sensory Working Memory , 2015 pp 187-200
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"... Neuronal Recordings in the PFC The lateral PFC (lPFC) was identified early on as an important neural substrate of visual short-term and recognition memory. Visual tasks that rely on short-term memory such as delayed response and DMS are severely impaired after bilateral lesions of the PFC . Neuronal activity in the PFC demonstrates visual short-term memory correlates by exhibiting sustained changes, often elevation, but sometimes suppression, during the retention interval of short-term memory tasks . Visual recognition memory is also apparent in the PFC primarily exhibiting match enhancement while some cells exhibit match suppression . The lPFC is hypothesized to be a general working/short-term memory area , but the difficulty in training monkeys to perform an auditory-only task assessing short-term and recognition memory has made the number of studies addressing the contribution of the PFC across modalities sparse . The lPFC receives multimodal information from a number of regions and auditory information from the anterolateral, mediolateral, and caudolateral parabelt areas of the superior temporal region and the medial geniculate nucleus of the thalamus . We have recently recorded from Brodmann’s area 46, including dorsal and ventral banks of the principal sulcus (i.e., lPFC) . We hypothesized that neurons in area 46 would encode both short-term and recognition memory as they do in visual tasks. Single-unit activity of lPFC (area 46) was recorded in monkeys performing the same DMS task as the dTP recording experiment described in the previous section. The analysis of single units indicated that the number of cells with activity changes increased on match versus nonmatch trials supported by a clear match enhancement effect starting at 200–300 ms in the population activity and continuing until the animal’s response ( Figure 2 ). The increase in cue 2 activity for matching stimuli compared with nonmatching stimuli, and in relation to cue 1, is a robust recognition memory correlate. The match enhancement correlate occurs later and is more robust than the early suppression recognition memory correlate seen in dTP. 2 ..."
Reference 20
Reference works Chapter
Animal Models of Amnesia
Alvarado M.C., Bachevalier J.
Learning and Memory: A Comprehensive Reference , 2017 pp 153-175
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"... Recognition Memory Two paradigms in particular have been used to assess recognition memory in rodents and monkeys: the delayed nonmatching-to-sample task (DNMS) and the visual paired comparison (VPC) task (also known as preferential looking, or spontaneous recognition). Like some tests of human recognition or recall, each task assesses whether subjects demonstrate that a given stimulus has been previously seen . However, substantial differences in the task requirements may alter both the demands made on memory processes and, potentially, the specific brain regions necessary for successful performance of each. In particular, these tasks may be seen as testing memory for “facts” as well as the duration of the memory trace, but with slight parametric modification. 3.10.4.1 Delayed Nonmatch to Sample This task was the first to successfully demonstrate a deficit in recognition memory consequent to the same neural damage that produces human amnesia. The task is simple in that monkeys learn to displace junk objects to obtain a hidden food reward. However, food is only located under objects that have not been seen recently. That is, animals are trained to associate novelty with reward. In the basic paradigm, the monkey is seated in a sound-attenuated chamber (Wisconsin General Testing Apparatus, or WGTA) behind an opaque screen. When the screen is raised, the monkey views a testing tray containing three equidistant food wells, which can be covered with junk objects, hiding either a baited or an empty well (see Fig. 3 in section The Neural Substrates of Memory: Earlier Studies ). Training takes place in two phases for each trial: sample and choice. During the sample phase, a single object covers the central food well, and when displaced, a food reward can be retrieved. The screen is then lowered and the now-familiar sample object is moved to cover a lateral well (empty), whereas a novel object covers the opposite lateral well (baited). After a brief period, typically ranging from 10 s to 10 min, the screen is raised, and the monkey must choose one of the objects. 2 ..."
Reference 21
Reference works Chapter
Recognition Memory (in Primates), Neural Basis of
E.A. Murray
International Encyclopedia of the Social & Behavioral Sciences , 2001 pp 12829-12832
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"... Neural Systems Mediating Visual Recognition For most sensory modalities (e.g., vision and touch), receptors convert sensory information into neural signals, and modality-specific cortical fields, such as the primary visual cortex (‘V1’ in Sect. Figure 1 ), process that information further. These early sensory processing stages are a prerequisite for recognition memory. However, the core recognition system must function more generally. If a blind person fails to recognize a visually presented object, we say that he or she has a visual impairment, not a failure of recognition memory. Therefore, this article will focus on general aspects of recognition and its neural basis, neglecting modality-specific ones. 1.1 Methods for Assessing Recognition Memory in Nonhuman Primates Because both human and nonhuman primates rely heavily on visual information in their daily activities, recognition is best understood for visible objects. Visual recognition memory in monkeys has been studied by making selective brain lesions and by disconnecting one brain region from another. These studies identify whether a given brain structure is critical for recognition. Monkeys, of course, cannot tell us whether they remember seeing an object. For this reason, methods have been developed that allow them to reveal that information. One commonly used method is the delayed nonmatching-to-sample task (DNMS). In DNMS, each trial has two parts: a sample presentation followed by a choice test. During the sample presentation, the monkey sees a single object, which covers the central well of a three-well test tray. The monkey then displaces the object to obtain a small piece of food hidden in the well underneath. A few seconds later the monkey sees the same, now-familiar object plus a novel one, with one object over the left well of the test tray and the other over the right well. The monkey can obtain more food by displacing the novel object but not by pushing aside the familiar one. Thus, on the choice test, the monkey solves the problem by applying a ‘nonmatching’ rule, i.e., by choosing the object that does not match the sample. 2 ..."
Reference 22
Book Chapter
Primate Models of Neurological Disease
Szabo Charles Akos
The Laboratory Primate , 2005 pp 467-486
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"... The apparatus was accessed by the macaque from its cage, and consisted of a tray with wells that could be baited with a food reward and covered by objects or cardboard plaques. A sliding door could be lowered between the animal and the tray in order to introduce progressive delays before it could respond to a stimulus. Computer-controlled tasks were performed with the sample and choices displayed on a large touch-sensitive screen that allowed animals to manually indicate their choices . The earliest paradigm to assess visual recognition memory in the Wisconsin General Testing Apparatus was the “matching-from-sample” paradigm. This procedure required the recognition of the similarity between the sample shape of an object and an identical shape presented in an array. This response was reinforced by a reward concealed under the matching shape. In the computer-generated adaptation of this test, enabling the generation of a large number of stimuli, a sample image is presented before it is compared to a novel choice object. The ability of the animal to remember the sample over time was then tested by delaying presentation of the sample and choice items for seconds to minutes. This paradigm was also able to test recognition of a list of up to 10 sample items presented sequentially . Other visuospatial memory tasks used to test working memory included the delayed spatial memory task, for which the animal had to remember which of two trays was baited, delayed spatial alternation tasks requiring the animal to alternate between sides on repeated trials, or delayed object alternation tasks rewarding the monkey when it learned to alternate between objects from one trial to the next ( Figure 28.1 ). The “non-matching-from-sample” paradigm, on the other hand, required that the animal learn a new condition or rule to be rewarded. This entailed the macaques identifying the novel choice object when presented with the “sample” or an object that it was already familiar with from a previous trial. More recently, computer-generated discrimination tasks were employed to study “object in place” and “object-reward association learning”, which have been shown to assess episodic memory in humans . 2 ..."
Reference 23
Book Chapter
Effects of Transcranial Electrical Stimulation on Sensory Functions
Chaieb L., Saiote C., Paulus W., Antal A.
The Stimulated Brain , 2014 pp 181-205
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"... Stimulation of temporal and parietal areas combined with visual stimulation Transcranial direct current stimulation seems to be an efficient tool for altering visual working memory performance in healthy humans. The effects have been most extensively tested for parietal and temporal cortex stimulation. However, the results of different studies are not completely consistent. Berryhill and colleagues explored the effects of tDCS over right inferior parietal regions on an object recognition and recall working memory task . tDCS was applied before task performance. In this study, cathodal stimulation impaired task performance. Clark and colleagues explored the impact of tDCS on identification of concealed objects, stimulating the right inferior frontal and right parietal areas. Here, anodal stimulation resulted in improved performance . Furthermore, this effect was dosage dependent, and its size was larger for naïve subjects as compared to experienced subjects . Bolognini and colleagues explored the effects of anodal tDCS applied to the posterior parietal cortex on multisensory field exploration . Stimulation of the right parietal cortex improved visual exploration and orienting, when compared to sham stimulation, supporting the causal involvement of this area in visual attentional processes. Recently, Flöel and co-workers demonstrated that anodal tDCS over the right temporo-parietal cortex improved memory consolidation in a task involving memorizing an object’s location in a natural surrounding . Chi and colleagues conducted a study which involved bilateral stimulation of the anterior temporal lobes during encoding and retrieval of a visual memory task . They found an improvement in visual memory using right anodal–left cathodal stimulation, but not under reversed polarity or sham stimulation conditions. Penolazzi and colleagues studied the impact of bilateral fronto-temporal stimulation on encoding of emotionally valenced pictures . Right anodal–left cathodal tDCS resulted in improved memory for emotionally pleasant pictures, while left anodal–right cathodal stimulation increased recall of emotionally unpleasant pictures. Taken together, many studies have been conducted in recent years in which the impact of tDCS on visual memory formation was explored. 2 ..."
Reference 24
Review article
Transcranial magnetic stimulation of visual cortex in memory: Cortical state, interference and reactivation of visual content in memory
van de Ven V., Sack A.T.
Behavioural Brain Research , 2013 pp 67-77
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"... In the first TMS study of memory in visual cortex , three participants completed a DMS task with different memory loads, in which they retained up to four visual items in memory for about half a second. Single-pulse TMS was administered over the occipital pole either during retention or after probe onset. TMS during the retention interval did not affect memory performance. On the other hand, TMS administered after probe onset increased the reaction time as a function of memory load (i.e., item scanning time), which suggested an interference of the memory matching process of single items in memory. More recent studies, however, have provided accumulating evidence that visual cortex supports memory retention. Silvanto and Soto administered TMS over occipital cortex during a change detection task of oriented gratings. Halfway at the retention interval of 2 s, participants were either briefly shown a distracting stimulus congruent (CON) or incongruent (INC) to the sample item, or no distracter at all (NO). This event was then followed by the presentation of a non-grating mask stimulus. A 10 Hz triple-pulse TMS train was presented at distracter onset (or, during NO trials, when the distracter would have been shown). After the retention interval, participants saw the memory probe and had to report if it matched the sample stimulus. In a non-TMS behavioral experiment participants reported seeing the distracter in less than 20% of the trials. Of these trials, INC distracters decreased memory accuracy, compared to CON and NO distracters. When TMS was administered, memory accuracy decreased for trials in which no distracters were shown, compared to trials with a distracter and to a sham TMS condition, which suggests that TMS affected a memory representation in visual cortex. At the same time, TMS improved performance on trials with INC distracters. Here, TMS may have interrupted the processing of the distracter, thereby inhibiting its otherwise interfering effect on memory performance. Similar effects have been reported in studies of visual perception, in which TMS disrupts the effect of visual masks presented shortly after target presentation [25,52] . 2 ..."
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"... Highlights ▸ We review TMS evidence that visual cortex plays a causal role in memory for visual events. ▸ Memory retention and consolidation alter cortical functional state of visual cortex. ▸ TMS can reactivate visual memory content in occipital cortex and hMT+ into awareness. ▸ Visual cortex contains a topographically organized neural representation of sensory information in memory. ▸ The neural mechanism of memory in visual cortex may be similar for different memory systems. 2 ..."
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"... A recent TMS study provided further support for this notion . Participants kept a visual image in mind for 2 s of a previously presented gratings at the center of fixation. Gratings were presented at one of three visual contrasts (10, 50 and 90%). A single TMS pulse was given at the end of retention at or slightly below phosphene threshold (PT) and participants had to indicate if they saw a phosphene. Overall, phosphene detection increased with the visual contrast of the grating (and, by inference, of the image of the grating), most notably so for phosphenes induced at a sub-PT intensity. More specifically, phosphene detection at sub-PT increased with increasing stimulus contrast. These findings thus indicate that stimulus contrast, and putatively contrast information of the mental image, affect cortical excitability of early visual cortex far beyond the temporal window of sensory stimulation. Thus, visual imagery and visual memory share functional resources from early visual cortices in similar ways, thereby demonstrating that the functional overlap between memory and perception are relevant for information processing. Whether the two cognitive functions exist on a continuum of mental representations or reflect distinct processes remains to be elucidated. 3 ..."
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"... Further evidence for a memory representation in early visual cortex comes from a study by our group . Participants completed a change detection task using small abstract shapes, in which the memory load varied between one and three simultaneously presented items across trials. A memory trial could be presented in one of the two hemifields. The TMS coil was positioned such that it affected processing of one hemifield, leaving the other as within-subject performance control. Single pulses were administered at 100, 200 or 400 ms into the retention interval. Results showed that TMS impaired memory performance when high load memory trials were presented in the visual field affected by TMS at 200 ms into the retention interval ( Fig. 2 A ). Similar results were obtained in a non-TMS behavioral version in which a distracter stimulus replaced the TMS pulses. Interestingly, this is the first study to show an effect of memory load in TMS interference of memory, which fits the notion of a capacity-limited short-term memory system [48,53] . Memory retention is more vulnerable to interference if the memory load approaches the capacity limit. Human fMRI studies showed a neural correlate for the capacity limitation of VSTM in frontal and parietal cortex [6,8] , in which brain activity increased monotonically with higher memory loads until the capacity limit was reached. Higher memory loads may then require more neural resources for memory retention, leaving fewer resources available to protect against interfering signals. Thus, these findings show that visual memory in early visual cortex is topographically organized and capacity-limited. Further, the findings suggest that short-term consolidation occurs early during retention, which coincides with psychophysical assessments of an early short-term consolidation window lasting up to 500 ms [53–55] . Another study by Silvanto and co-workers provided further support for an early short-term consolidation window in visual cortex . Single TMS pulses were delivered over occipital cortex at the onset or end of the retention of visual clock hands in memory. Results showed that TMS at retention onset delayed response times, compared to TMS at the end of retention. 3 ..."
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"... In other words, interference of memory formation occurred only if training in the TMS quadrant was separated by an alternative task in another spatial location. These findings suggest that a TMS-interference effect per se on memory formation in visual cortex may be too simplistic an interpretation of skill acquisition in the brain. Rather, we interpreted these findings as evidence of vulnerability of memory formation in early visual cortex as a function of current functional brain state that includes other (higher-order) areas. Although a controversial finding, it appears to coincide with reports of changes in functional coupling between visual cortex and non-sensory brain areas distributed across the brain [93–96] . In summary, these studies have shown that TMS over occipital cortex may interfere with sensory memory formation that normally occurs at a time scale of multiple days. Particularly, De Weerd et al. showed that rTMS delivered at a time period well after active training ended interrupted memory consolidation. This finding fits with neurophysiological results of ongoing metabolic, synaptic and molecular changes that contribute to the consolidation of memory [96,97] . Crucially, the offline TMS effect rules out the possibility that the learning impairment resulted from interrupted cognitive control or mental imagery performance. Instead, the results provide strong support for a neural representation of memory in early visual cortex. Conversely, it is possible that such a neural representation of memory contributes to the retention of sensory information in visual short-term memory. Application of TMS pulses could interfere with the ongoing activity or functional coupling with higher order areas, thereby interfering with the maintenance of information in visual cortex. 3 ..."
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"... Memory reactivation TMS can also be used to reactivate memory representations in sensory cortex. Penfield and Perot had shown that it is in principle possible to use brain stimulation to reactivate episodic memories into awareness, with a degree of perceptual quality that resembled true sensory experiences. Further, it has been shown that retrieval of autobiographical events from memory reactivates sensory brain areas that were also involved in the initial encoding of the sensory experiences . Neurophysiological studies in rats and non-human primates have also shown that memory consolidation during sleep involves reactivation of ‘scripts’ of sensory cortical activity [93,96] . In light of these findings, it is plausible that local brain stimulation using TMS could result in reactivation of memory representations into awareness. Currently, three TMS studies have pursued this intriguing approach. In all studies, TMS pulses were administered over visual cortex in order to induce perceptual experiences that are reminiscent of the actual sensory perceptions. Key to these studies is the induction of phosphenes with TMS. Phosphenes induced by occipital cortex stimulation likely include activity in early visual cortex [32,33] . Further, the cortical excitability of early visual cortex, as a result of sensory or cognitive context , affects phosphene perception. These characteristics could thus make phosphenes a useful TMS tool to investigate memory in early visual cortex. Silvanto et al. had participants visually adapt to an iso-luminant colored surface. After adaptation, participants saw an after-image in the opposite color when looking at a black screen. However, TMS-induced phosphenes were of the adapted-to color, rather than the color of the after image. Thus, TMS reactivated the weaker color representation in occipital cortex. Further experiments showed that phosphene-induced ‘reactivation’ of the adapted color facilitated detection of the adapted color, which normally is harder to detect. 4 ..."
Reference 25
Reference works Chapter
Amnesia
Lafleche G., Verfaellie M.
Encyclopedia of Applied Psychology , 2004 pp 129-138
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"... There have been several reported cases of bilateral PCA infarction that spared the medial temporal lobes proper but that involved the occipital lobes bilaterally as well as the deep white matter of both the occipital and temporal lobes. These patients present with a visual amnesic syndrome that results from the disconnection between occipital cortices involved in visual processing and temporal brain regions supporting memory. There have been other reported cases in which the PCA infarction was unilateral. Patients with infarction of the left PCA present with a selective verbal memory deficit, whereas patients with infarction of the right PCA have preserved verbal memory but impaired visual processing skills and impaired visual memory. Amnesia can also be caused by thalamic infarction. In such cases, the severity of the memory impairment is related to the site of damage within the thalamus. Lesions that damage the mammillo–thalamic tract, in particular, have been associated with severe anterograde amnesia. Infarction of the medial dorsal thalamic nuclei has also been associated with memory impairments, but it appears that the damage must extend beyond the medial dorsal nucleus to include the mammillo–thalamic tract or anterior nucleus for the development of a severe amnesic disorder. Because the thalamus has rich connections with the frontal lobes, this anterograde amnesia is also accompanied by an increased sensitivity to interference and by impairments in executive functioning. As with other amnesic syndromes, left-sided lesions result in impairments on tasks of verbal learning, whereas right-sided lesions result in nonverbal/visual memory impairments. Retrograde memory deficits following thalamic infarction are variable; some patients are found to have little impairment in remote memory, whereas others demonstrate severe long-term memory impairments. 5.2.3 Wernicke–Korsakoff Syndrome Wernicke–Korsakoff syndrome (WKS) is seen in patients with a history of long-term alcohol abuse in association with poor nutrition and a lack of Vitamin B1 (thiamine). 3 ..."
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"... Patients with infarction of the left PCA present with a selective verbal memory deficit, whereas patients with infarction of the right PCA have preserved verbal memory but impaired visual processing skills and impaired visual memory. Amnesia can also be caused by thalamic infarction. In such cases, the severity of the memory impairment is related to the site of damage within the thalamus. Lesions that damage the mammillo–thalamic tract, in particular, have been associated with severe anterograde amnesia. Infarction of the medial dorsal thalamic nuclei has also been associated with memory impairments, but it appears that the damage must extend beyond the medial dorsal nucleus to include the mammillo–thalamic tract or anterior nucleus for the development of a severe amnesic disorder. Because the thalamus has rich connections with the frontal lobes, this anterograde amnesia is also accompanied by an increased sensitivity to interference and by impairments in executive functioning. As with other amnesic syndromes, left-sided lesions result in impairments on tasks of verbal learning, whereas right-sided lesions result in nonverbal/visual memory impairments. Retrograde memory deficits following thalamic infarction are variable; some patients are found to have little impairment in remote memory, whereas others demonstrate severe long-term memory impairments. 5.2.3 Wernicke–Korsakoff Syndrome Wernicke–Korsakoff syndrome (WKS) is seen in patients with a history of long-term alcohol abuse in association with poor nutrition and a lack of Vitamin B1 (thiamine). In acute Wernicke’s encephalopathy, patients exhibit confusion, a gait disorder (ataxia), and abnormal eye movements (oculomotor palsy). Treatment with large doses of thiamine may result in improvement in, or even reversal of, some of these symptoms. However, most patients are left with a permanent dense amnesic disorder referred to as Korsakoff’s syndrome. This amnesic syndrome arises from damage to the thalamic nuclei, the mammillary bodies, and the frontal system. 3 ..."
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"... Because the thalamus has rich connections with the frontal lobes, this anterograde amnesia is also accompanied by an increased sensitivity to interference and by impairments in executive functioning. As with other amnesic syndromes, left-sided lesions result in impairments on tasks of verbal learning, whereas right-sided lesions result in nonverbal/visual memory impairments. Retrograde memory deficits following thalamic infarction are variable; some patients are found to have little impairment in remote memory, whereas others demonstrate severe long-term memory impairments. 3 ..."
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"... In acute Wernicke’s encephalopathy, patients exhibit confusion, a gait disorder (ataxia), and abnormal eye movements (oculomotor palsy). Treatment with large doses of thiamine may result in improvement in, or even reversal of, some of these symptoms. However, most patients are left with a permanent dense amnesic disorder referred to as Korsakoff’s syndrome. This amnesic syndrome arises from damage to the thalamic nuclei, the mammillary bodies, and the frontal system. Patients with WKS suffer from both anterograde and retrograde amnesia. Several explanations have been proposed to account for their episodic memory impairment. Although early models emphasized their superficial and deficient encoding strategies or their failure to inhibit competition from irrelevant material at the time of retrieval, current views agree that an explanation of their learning deficits is best accounted for by a theory that integrates both encoding and retrieval processes. The retrograde amnesia in WKS has a steeper temporal gradient than that found in medial temporal lobe amnesia. The concomitant presence of frontal dysfunction in Korsakoff’s patients is believed to account for their poorer performance on remote memory tests. Intelligence is usually preserved in Korsakoff’s patients, but there are often associated cognitive and neurobehavioral deficits that are unique to this patient population. In particular, some combination of impaired planning and initiation, passivity, apathy, confabulation, and limited insight is nearly always found. These symptoms are thought to arise from associated frontal dysfunction. 3 ..."
Reference 26
Reference works Chapter
Amnesia
Lafleche G., Palombo D.J.
Reference Module in Neuroscience and Biobehavioral Psychology , 2017
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"... Stroke Amnesia is a common consequence of infarction of the posterior cerebral artery (PCA). It results from neural tissue damage caused by the interruption of blood flow to a large part of the medial temporal lobes, particularly the posterior two-thirds of the hippocampus, the parahippocampal gyrus, and other critical pathways that connect the hippocampus to surrounding brain areas. A more posterior extension of the lesion will result in other neuropsychological deficits in addition to memory disturbance, for example, visual field defects and other visual disturbances that may affect reading and cause problems with color identification, space perception, and/or object naming. The typical memory disturbance associated with bilateral PCA infarction is an inability to establish new memories (anterograde amnesia) in the presence of preserved intelligence and attention. Retrograde memory problems are also often present, as in other amnesic cases. There have been several reported cases of bilateral PCA infarction that spared the medial temporal lobes proper but that involved the occipital lobes bilaterally, as well as the deep white matter of both the occipital and temporal lobes. These patients present with a visual amnestic syndrome that results from the disconnection between occipital cortices involved in visual processing and temporal brain regions supporting memory. There have been other reported cases in which the PCA infarction was unilateral. Patients with infarction of the left PCA present with a selective verbal memory deficit, whereas patients with infarction of the right PCA have preserved verbal memory but impaired nonverbal/visual memory. Amnesia can also be caused by thalamic infarction. In such cases, the severity of the memory impairment is related to the site of damage within the thalamus. Lesions that damage the mammillo–thalamic tract, in particular, have been associated with severe anterograde amnesia. Infarction of the medial dorsal thalamic nuclei has also been associated with memory impairments, but it appears that the damage must extend beyond the medial dorsal nucleus to include the mammillo–thalamic tract or the anterior nucleus for the development of a severe amnesic disorder. 3 ..."
Reference 27
Book Chapter
Posterior Cerebral Artery Disease
James C. Grotta, Gregory W. Albers, Joseph P. Broderick, Arthur L. Day, Scott E. Kasner, Eng H. Lo, Ralph L. Sacco, Lawrence K.S. Wong, Jong S. Kim
Stroke , 2022 pp 347-367.e6
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"... Tuberothalamic (Polar) Artery Territory Infarction The tuberothalamic artery originates from the middle-third of the posterior communicating artery. In approximately one-third of the normal population, this territory is supplied by the paramedian artery that arises from the P1 portion of the PCA (see Fig. 25.7 ). 96 The tuberothalamic arteries mainly supply the ventral anterior nucleus (VA), rostral part of the VL, and the ventral pole of the medial dorsal nucleus (MD). It seems that the anterior nuclear group is supplied by both the tuberothalamic and choroidal arteries. The main clinical syndromes that result from tuberothalamic infarction include neuropsychological deficits. In the early stages of infarction, patients exhibit fluctuating levels of consciousness and appear withdrawn. Patients show impaired recent memory formation, which is more prominent when left-sided lesions are present. Visual memory impairments more often develop with right-sided lesions. 96 , 97 Amnestic syndrome seems to be caused by the disconnection of memory circuitry (e.g., between the VA and the hippocampal formation or amygdala). 98 , 99 Language disturbances also occur in patients with left-side infarction. This is characterized by anomia with decreased verbal output and impaired fluency, impaired comprehension, and paraphasic speech. Reading and repetition are relatively preserved. Left thalamic lesions are also associated with acalculia. Constructional, buccofacial, and limb apraxia may present (more often with left-sided lesions), whereas hemineglect may present in patients with right-side infarction. Patients may develop persistent personality changes, including euphoria, lack of insight, apathy, and lack of spontaneity. 97 , 100 , 101 Hypometabolism in the posterior cingulate cortex of these patients, as assessed by positron-emission tomography, suggests that these behavioral changes may be related to thalamocortical disconnection. 101 3 ..."
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"... 144–146 Theoretically, there are two forms of visual agnosia: the “apperceptive” form that is caused by impaired visual processing that results in the poor perception of the object, and the “associative” form that is caused by disorders that affect the associative cortex and results in the correctly formed visual percepts being poorly matched with previously processed sensory data and recognition. 147 , 148 Most patients with visual agnosia present with both aspects, although one type may predominate. There appear to be multiple pathophysiologic mechanisms that result in apperceptive visual agnosia. These may be related to the misperception of shapes due to defects in representing the elementary properties of curvature, surface, and volume 149 or failure to integrate multiple elements into a perceptual whole. 150 Patients with severe apperceptive agnosia usually have extensive and diffuse occipital lesions and tend to have residual field defects. 151 Closely related to the associative form of visual agnosia is optic aphasia, in which patients are unable to name visually presented objects but otherwise show relatively intact knowledge about objects and are, thereby, able to categorize and demonstrate their use through pantomime. 152 , 153 Visual agnosia and optic aphasia may simply represent a continuum with varying deficits in knowledge retrieval. 154 , 155 Patients typically present with large left PCA territory infarction with right homonymous hemianopia. 152–154 , 156 , 157 It has been suggested that there is a functional disconnection between visual perception and language systems. Prosopagnosia Prosopagnosia is the inability to recognize previously familiar faces. 158 The deficit is mostly restricted to the identification of faces, but some patients have difficulty recognizing other objects such as animals, cars, buildings, food, or clothing. 159–163 Many patients can perceive gender, age, and recognize facial expressions. 164 , 165 Some patients are unable to process the general features of objects, such as curved surfaces and spatial configurations, which is particularly important when discriminating faces. 3 ..."
Reference 28
Reference works Chapter
Agnosia (including Prosopagnosia and Anosognosia)
Berti A., Neppi-Modona M.
Encyclopedia of Human Behavior , 2012 pp 60-67
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"... Visual Agnosia: Overview Visual agnosia refers to the general impairment of stimulus recognition in the visual modality in the absence of perceptual deficits, memory problems, and general intellectual impairment. Individuals with visual agnosia demonstrate normal recognition of objects through modalities other than vision (touch, audition, and verbal description of objects function). Agnosia does not necessarily impair the recognition of all visual stimuli, but can selectively affect certain categories of percepts (objects, faces, colors, written words, body parts, environmental scenes), leaving others intact. Patients are well aware of their predicament. In 1889, Freund, a German neurologist of Breslau, described a case of visual recognition deficit that he named optic aphasia and he interpreted as a consequence of the disconnection of visual from language areas. A year later (1890), Lissauer, a colleague of Freund, published a paper where he clearly distinguished two different forms of agnosia: apperceptive agnosia, or inability to construct a good perceptual representation from the visual input, and associative agnosia, or inability to access the stored knowledge related to the percept. Despite these two authors being the first to report documented cases of agnosia, the term agnosia was coined by Freud in 1891 to describe object recognition problems in some individuals. Although it is a relatively rare neurological symptom, with some 100 cases published between 1890 and 1990, its study has greatly contributed to our understanding of how the process of visual recognition is organized in the human brain. As already mentioned, the most common form of agnosia is agnosia for objects, but forms of agnosia specific for a category of objects are also possible (e.g., agnosia for faces (prosopagnosia), agnosia for colors (color agnosia), agnosia for words (pure alexia or agnosic alexia), agnosia for scenes). Here, we briefly review these different forms of agnosia. 3 ..."
Reference 29
Book Chapter
Disorders of Higher Cortical Visual Function
Victoria S. Pelak
Liu, Volpe, and Galetta's Neuro-Ophthalmology , 2019 pp 341-364
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"... Visual Agnosias A visual object agnosia is an inability to recognize visualized objects despite relatively normal vision, memory, language, and intellectual function. 75,76 In this condition, naming function is intact; patients are able to identify objects by touching and feeling them or by listening to a verbal description. 77 Functional neuroimaging and case studies suggest shapes and textures are processed separately in the lateral occipital (LO) and collateral sulcus (CS) regions, respectively, to recognize objects ( Fig. 9.6 ). 78,79 Classically, a distinction between associative and apperceptive agnosias is made. 80–82 Associative visual object agnosia . Patients with this type of agnosia have relatively normal vision within intact visual fields. They are able to draw or copy what they see, indicating their perception is relatively normal. 28 Upon request, they can also produce accurate drawings of objects they are unable to recognize visually, indicating intact visual memory and imagery. 28 Associative visual object agnosia suggests bilateral medial inferior occipitotemporal lesions disrupting the inferior longitudinal fasciculus, 83,84 a white matter pathway connecting striate cortex with visual association areas in the temporal lobe. This is usually due to bilateral posterior cerebral artery occlusion and produces a “visual–verbal disconnection syndrome.” 85 Many cases of associative visual object agnosia also exhibit alexia without agraphia, 28,86 likely reflecting concomitant involvement of the corpus callosum in such instances. 83 Many are also associated with prosopagnosia (see later discussion). 28 Less commonly, isolated unilateral left or right hemispheric lesions can produce associative visual object agnosia. 86 Apperceptive visual object agnosia . In this type, also termed visual form agnosia, patients have confounding deficits in shape and form perception, although elemental acuity and fields are still relatively normal. 75,87 For instance, patients with apperceptive visual agnosia have difficulty copying geometric figures. In one study, 88 patients also had difficulty recognizing and naming line drawings, recognizing complex shapes, and mentally manipulating objects by rotation, for instance. 3 ..."
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"... Patients with this type of agnosia have relatively normal vision within intact visual fields. They are able to draw or copy what they see, indicating their perception is relatively normal. 28 Upon request, they can also produce accurate drawings of objects they are unable to recognize visually, indicating intact visual memory and imagery. 28 Associative visual object agnosia suggests bilateral medial inferior occipitotemporal lesions disrupting the inferior longitudinal fasciculus, 83,84 a white matter pathway connecting striate cortex with visual association areas in the temporal lobe. This is usually due to bilateral posterior cerebral artery occlusion and produces a “visual–verbal disconnection syndrome.” 85 Many cases of associative visual object agnosia also exhibit alexia without agraphia, 28,86 likely reflecting concomitant involvement of the corpus callosum in such instances. 83 Many are also associated with prosopagnosia (see later discussion). 28 Less commonly, isolated unilateral left or right hemispheric lesions can produce associative visual object agnosia. 86 Apperceptive visual object agnosia . In this type, also termed visual form agnosia, patients have confounding deficits in shape and form perception, although elemental acuity and fields are still relatively normal. 75,87 For instance, patients with apperceptive visual agnosia have difficulty copying geometric figures. In one study, 88 patients also had difficulty recognizing and naming line drawings, recognizing complex shapes, and mentally manipulating objects by rotation, for instance. The exact anatomic substrate is unclear, but some neuroimaging and PET studies have demonstrated lesions or hypoperfusion in bilateral temporooccipital cortices. 89–91 One patient with a closed head injury developed an apperceptive agnosia and prosopagnosia from selective damage to the right lateral fusiform gyrus. 92 A number of cases of apperceptive visual agnosia have been reported following carbon monoxide toxicity, 29,93 which has a predilection for causing occipital lobe damage. 3 ..."
Reference 30
Book Chapter
Higher-Order Visual Impairments
Alexander M.P.
Office Practice of Neurology , 2003 pp 895-902
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"... Patients with large left-sided unilateral lesions continue to have more clear-cut visual-language deficits (alexia and optic aphasia) and general language deficits (anomic aphasia) and less perceptual recognition impairment. Prosopagnosia Prosopagnosia is defined by an inability to recognize familiar faces despite preservation of adequate acuity. Prosopagnosia usually is caused by bilateral lesions in inferior temporo-occipital cortex, most commonly infarcts. It has also been described in patients with focal progressive atrophy of the right temporal lobe, probably a variant of frontotemporal dementia. Patients with infarcts have superior altitudinal visual field deficits ( Table 141-4 ). Achromatopsia is also commonly seen. Depending on lesion extent in medial temporal regions, there may be considerable memory impairment. Some patients have only large right temporo-occipital lesions. They usually have left hemianopia and impaired topographic memory. With either lesion configuration, impairments in other perceptually demanding visual discriminations have been reported, most notably a farmer unable to distinguish between the cows in his dairy herd. Note that prosopagnosia can be considered a modality-specific loss of knowledge. Normal rapid facial recognition appears to be a global perceptual task. In normal subjects the right hemisphere is faster and more reliable at recognizing familiar faces than the left. Permanent prosopagnosia is less common after unilateral right lesions than after bilateral injuries. This suggests that the right ventral occipitotemporal association cortex may be the critical processing node but that in most patients the left posterior association cortex can extract enough perceptual information for recognition, even if slowly. Testing for prosopagnosia takes some planning. Because it is a visual modality-specific deficit, the examiner must be careful to provide only visual information. Magazine pictures or family pictures are useful. If real people (i.e., family members) are used for testing, they must be cautioned not to speak or to wear distinctive clothing. This is not a test of perception that happens to use faces. It is a test of recognition of familiar, known faces. 3 ..."
Reference 31
Handbook Chapter
Neuro-ophthalmology
Alfredo A. Sadun, Michelle Y. Wang
Handbook of Clinical Neurology , 2011 pp 117-157
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"... Advanced Alzheimer's disease Patients with more severe AD may demonstrate various profound impairments of vision, including visual acuity in the 20/100–20/400 range, visual field defects, dyschromatopsia, decreased contrast sensitivity across all spatial frequencies, lack of stereopsis, visual attention, visual memory testing, and markedly abnormal eye movements and visual-evoked potentials . Neurodegeneration in both afferent and cortical visual pathways appears to play a central role in the visual sensory dysfunction in AD. Given that neurodegeneration in AD may involve the entire visual pathway, from the RGCs to the higher processing visual cortex, visual dysfunction may worsen vision-dependent tasks such as simple or complex pattern recognition, attention, memory, and spatial localization . Associations Bálint's syndrome, a rare ocular disorder characterized by simultanagnosia (difficulty identifying objects in a simultaneously displayed visual scene due to limited attention), ocular ataxia (misreaching under visual guidance), and ocular motor apraxia (inability to make accurate horizontal saccades to a target), has been associated with AD . An association between AD and positive visual phenomena has also been documented . Neuroimaging Structural imaging, such as CT or MRI, may show in AD cerebral atrophy predominantly in the occipitoparietal and occipitotemporal areas . Functional imaging, such as positron emission tomography or single-photon emission CT, might show decreased metabolism in the parietal or occipital cortex. Because of these associations, neuroimaging may be helpful in making the diagnosis of optic neuropathy of AD. Conclusion Neurologists and ophthalmologists should be aware that AD-associated optic neuropathy has been often overlooked given the complexities of the other dysfunctions. However, recognition of the visual manifestations of this neurodegenerative disorder may help identify the cause of the symptoms. Suspicion should be raised for older patients with or without a history of AD and persistent visual complaints not attributable to structural eye problems . 3 ..."
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"... The visual field in AD may be relatively preserved initially, but as the disease progresses various patterns such as inferior arcuate visual field defects, peripheral constriction, and homonymous hemianopsias may occur . Advanced Alzheimer's disease Patients with more severe AD may demonstrate various profound impairments of vision, including visual acuity in the 20/100–20/400 range, visual field defects, dyschromatopsia, decreased contrast sensitivity across all spatial frequencies, lack of stereopsis, visual attention, visual memory testing, and markedly abnormal eye movements and visual-evoked potentials . Neurodegeneration in both afferent and cortical visual pathways appears to play a central role in the visual sensory dysfunction in AD. Given that neurodegeneration in AD may involve the entire visual pathway, from the RGCs to the higher processing visual cortex, visual dysfunction may worsen vision-dependent tasks such as simple or complex pattern recognition, attention, memory, and spatial localization . 3 ..."
Reference 32
Handbook Chapter
The temporal lobe in typical and atypical Alzheimer disease
Migliaccio R., Cacciamani F.
Handbook of Clinical Neurology , 2022 pp 449-466
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"... After visuoperceptual processing in the occipital cortex (e.g., treatment of object size and orientation), in the temporal lobe, the stimulus is compared to mental representations previously stored in long-term memory. At the end of this process, the individual will have correctly perceived the visual characteristics of the stimulus, recognized its function, the context where it can be found, its use, etc. (for a discussion on the role of large-scale networks in object representation, see also Mahon, this volume). In clinical examination, visual agnosia is often observed in naming tasks. Patients with impaired visual recognition can still name the target objects on tactile or acoustic presentation (see Bartolomeo, this volume). Patients with AD dementia also have difficulty recognizing people, a condition known as prosopagnosia. Anosognosia is a condition in which a patient ignores some of his/her own deficits, underestimates their impact on activities of daily living, or is completely unaware of being affected by a disease. A large proportion of patients with AD dementia are unaware of their cognitive and behavioral impairment, especially those with amnestic and dysexecutive (i.e., frontal) profiles . Anosognosia depends on damage to the prefrontal cortex, medial temporal lobe, and temporal-occipito-parietal junction, especially in the right hemisphere. A dysfunction of the mid-temporal regions would cause memory disorders, compromising the ability to compare the current performance with previous ones . Damage to the prefrontal and inferior parietal cortices has also been associated with anosognosia in AD . The first is indeed involved in error detection and online performance monitoring, the second underlies the ability to evaluate one's performance by taking a third-person point of view. Psycho-behavioral disorders are also characteristic of typical AD dementia, but they are less frequently present in predementia stages . Patients may have delusional beliefs, worsened by agnosic disorders that do not allow a correct perception of reality. Common delusions are paranoid ideas of persecution and spouse's infidelity. 3 ..."
Reference 33
Review article
Vision function abnormalities in Alzheimer disease
Tzekov R., Mullan M.
Survey of Ophthalmology , 2014 pp 414-433
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"... Visual memory Tests of visual memory indicate that this function is significantly affected in AD even before the appearance of other clinical symptoms and thus could have a predictive value for the development of the disease. Performance on the Benton Visual Retention Test, which measures visual perception, vision memory, and visuoconstructive abilities, was significantly predictive of AD development in two, relatively large, population-based longitudinal studies. In the first, 1,425 participants older than 60 years living in the Baltimore, Maryland, area were tested several times and patients who made six or more errors on the test had a significantly higher risk in developing AD up to 15 years after testing (similar finding in a smaller cohort [n = 371] were reported earlier 321 ), but before the diagnosis of AD. 147 Similarly, in the second study, testing 1,265 non-demented patients older than 65 years living in southwestern France six times during a 10-year period revealed that participants who did not develop AD had a relatively high score that was stable over time, whereas future AD patients had a significantly lower score that decreased during the observation period. 4 3 ..."
Reference 34
Book Chapter
Disorders of Higher Cortical Function
Berti A., Garbarini F., Neppi-Modona M.
Neurobiology of Brain Disorders , 2015 pp 525-541
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"... Disorders of Visual Recognition: Agnosia The neuropsychological disorder known as agnosia refers to the impairment of stimulus recognition in one modality in the absence of perceptual deficits, memory problems, and general intellectual impairment. This disorder is intriguing both scientifically and clinically and its study has contributed to shedding light on how the normal visual system functions. When the impaired recognition relates to objects in general, the condition is called object agnosia; when the unrecognized visual stimulus is a face, it is called prosopagnosia. An overview of the major types of agnosia is presented here. Object Agnosia In object agnosia, patients do not recognize objects in one specific input modality (visual, tactile, or auditory), whereas the same objects can be promptly recognized when presented through a different input channel. The perceptual nature of the disorder is testified by the fact that it cannot be ascribed to the co-occurrence of sensory elementary deficits, memory problems, naming difficulties (aphasia), and general intellectual impairment (patients are well aware of their predicament). Visual Agnosia Although it is a relatively rare neurological symptom, with some 100 cases published between 1890 and 1990, its study has greatly contributed to the understanding of how the process of visual recognition is organized in the human brain. There is no standard taxonomy of visual agnosias, but most neuropsychologists agree with Lissauer’s original distinction between apperceptive and associative types, 34 depending on the lower or higher processing stage of visual information affected by the brain lesion. Because this account has continued to be used in the neuropsychological literature to the present day, it is used here as a general framework. Apperceptive Agnosia Apperceptive agnosia is evident when patients are unable to recognize objects because they cannot see them properly, in the absence of elementary visual deficits. It is thought to arise from a breakdown at relatively early stages of visual processing, where the elementary features of the stimulus are analyzed. Object recognition through verbal description by the examiner is, instead, preserved. 3 ..."
Reference 35
Handbook Chapter
Bilateral parietal dysfunctions and disconnections in simultanagnosia and Bálint syndrome
Chechlacz M.
Handbook of Clinical Neurology , 2018 pp 249-267
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"... Disorientation and other problems General visuo(spatial) disorientation is often added to the triad of symptoms associated with Bálint syndrome. While some authors previously used the term visual disorientation as a synonym for simultanagnosia , others argue whether this problem should or should not be treated separately from simultanagnosia, especially as some evidence suggests that both symptoms rely on overlapping cognitive mechanisms . Deficits in visual memory and stereoscopic vision are often reported in Bálint syndrome, and add to problems associated with daily living, experienced by patients . In line with current understanding of Bálint syndrome, while deficits in memory and stereopsis are not regarded as factors underlying core symptoms, testing for visual working memory and depth perception is considered essential for accurate diagnosis . Recent work suggests that visuospatial working-memory impairments, in particular severely affected ability to maintain spatial representation of visual information, likely contribute to the inability to judge positional relationships between different elements of the visual scene, and subsequently to deficits in accurately navigating in space and executing movements towards a different object. Thus, it is plausible that visuospatial working-memory shortfalls shape the behavior of patients with Bálint syndrome, including bumping into objects or other people and getting easily lost even in their own home or other familiar spaces . Furthermore, another recent study indicates that impaired visuospatial working memory affecting ability to maintain a saliency map over time may result in chaotic ocular exploration in Bálint syndrome . 3 ..."
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"... Interestingly, it has been shown that, though simultanagnosia patients are typically poor at explicitly reporting global forms, there is also evidence that global processing may take place implicitly. Finally, it has been shown that deficits in hierarchic processing in simultanagnosia result from a failure of flexible top-down attention . It is also worth noting that a series of experiments by Coslett and Lie (2008b) have suggested that in some simultanagnosic patients the ability to report more than one object in a two-object array might be affected by the semantic relationship between presented objects (increased performance with presentation of two semantically related objects) and repetition blindness (worse performance with presentation of two identical objects; Coslett and Lie, 2008b ). Disorientation and other problems General visuo(spatial) disorientation is often added to the triad of symptoms associated with Bálint syndrome. While some authors previously used the term visual disorientation as a synonym for simultanagnosia , others argue whether this problem should or should not be treated separately from simultanagnosia, especially as some evidence suggests that both symptoms rely on overlapping cognitive mechanisms . Deficits in visual memory and stereoscopic vision are often reported in Bálint syndrome, and add to problems associated with daily living, experienced by patients . In line with current understanding of Bálint syndrome, while deficits in memory and stereopsis are not regarded as factors underlying core symptoms, testing for visual working memory and depth perception is considered essential for accurate diagnosis . Recent work suggests that visuospatial working-memory impairments, in particular severely affected ability to maintain spatial representation of visual information, likely contribute to the inability to judge positional relationships between different elements of the visual scene, and subsequently to deficits in accurately navigating in space and executing movements towards a different object. Thus, it is plausible that visuospatial working-memory shortfalls shape the behavior of patients with Bálint syndrome, including bumping into objects or other people and getting easily lost even in their own home or other familiar spaces . 3 ..."
Reference 36
Book Chapter
Mild cognitive impairment
Paul Johns
Clinical Neuroscience , 2014 pp 145-162
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"... Visuospatial problems Patients with Alzheimer's disease often get lost in familiar places and may forget where they have left things. These features, together with impaired recall of daily events, reflect severe pathology in the medial temporal lobe. This involves structures such as the entorhinal cortex and hippocampus that are involved in spatial navigation and formation of episodic memories (see Ch. 3 ). Other visuospatial problems are due to abnormalities of the temporal and parietal association areas. Parietal lobe pathology may interfere with the ability to understand spatial relationships and manipulate objects, making it difficult to carry out ordinary daily tasks like getting dressed. Degeneration of the temporal neocortex may affect visual recognition of objects and people (including close friends and family members). 3 ..."
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"... Clinical aspects The diagnosis of Alzheimer's disease is predominantly clinical and post-mortem studies suggest that it is correct in at least 80% of cases. Two variants of Alzheimer's disease that might cause diagnostic confusion are discussed in Clinical Box 12.3 . Memory loss Loss of short-term memory is a prominent, early feature. Patients may ask the same question repeatedly or forget recent conversations and events. The ability to take in new information is affected first, with relative preservation of long-term memories and knowledge. Recollection of personal experiences ( episodic memory ) is particularly affected. Since the onset is insidious, this may initially be mistaken for normal age-related forgetfulness. As the disease progresses, earlier memories are gradually eroded and ultimately patients are unable to recall key details of their own lives. Visuospatial problems Patients with Alzheimer's disease often get lost in familiar places and may forget where they have left things. These features, together with impaired recall of daily events, reflect severe pathology in the medial temporal lobe. This involves structures such as the entorhinal cortex and hippocampus that are involved in spatial navigation and formation of episodic memories (see Ch. 3 ). Other visuospatial problems are due to abnormalities of the temporal and parietal association areas. Parietal lobe pathology may interfere with the ability to understand spatial relationships and manipulate objects, making it difficult to carry out ordinary daily tasks like getting dressed. Degeneration of the temporal neocortex may affect visual recognition of objects and people (including close friends and family members). Reasoning and language As with most forms of dementia, there is a general decline in problem-solving ability and abstract reasoning which impairs decision-making and judgement. This affects the capacity to manage personal affairs without supervision and interferes with ordinary daily activities such as shopping, cooking and paying bills. Language problems are very common, with word-finding difficulties and reduced verbal fluency in the initial stages, sometimes progressing to almost complete loss of verbal communication in advanced dementia. Psychiatric features Early in the course of the disease, patients tend to become withdrawn and may experience depression or anxiety . 3 ..."
Reference 37
Book Chapter
Computerized Cognitive Retraining Programs for Patients Afflicted with Traumatic Brain Injury and Other Brain Disorders
Mukundan C.R.
Neuropsychological Rehabilitation , 2013 pp 11-32
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"... Visuospatial Analysis and Synthesis Examination of visual space and its analysis for the purpose of recognition of spatial attributes is an important domain for cognitive retraining of patients who have significant right-hemisphere damage or dysfunction. Visuospatial analysis and visual integration are important cognitive abilities required to differentiate and recognize visuospatial attributes of objects and to use the visual space in which one lives and works. Such visual-perceptual errors are different from a total failure of visual recognition identified as visual agnosia. Visual-perceptual and integrative failures are easily detected in neuropsychological performance tests, namely, block design test, object assembly test, Alexander’s pass-along test, complex figure test, Bender Gestalt test, and other visuospatial drawing and construction tests. Loss or impairment in visuospatial functions can cause difficulties for the individual in spatial orientation in movements, impairments in spatial coordination, perceptual assessment of relative size of objects, spatial distances and positions, and other spatial attributes, all of which can disturb sensorimotor contacts with reality. Retraining in visuospatial perception and coordination can be easily carried out by the use of computerized programs. However, it may not be appropriate to presume that retraining in the two-dimensional video-space of the computer screen will automatically help restore the lost functional capabilities, especially those related to psychomotor handling of real personal space. The BFT has programs which help to distinguish differences in size and patterns using direct comparison and working memory paradigms. Visual-perceptual impairments generally occur in TBI cases as well as lesions of occipital–parietal–temporal lobes. Retraining using exposure time of the target patterns for long to very short durations helps the individual learn to differentiate and recognize patterns in a rapid manner. Tests of visual perception incorporating pattern construction and drawing are important ingredients of any neuropsychological battery of tests. The BFT program allows perceptual discrimination based on size and pattern complexity. 3 ..."
Reference 38
Review article
Cholinergic modulation of sensory perception and plasticity
Kunnath A.J., Gifford R.H., Wallace M.T.
Neuroscience & Biobehavioral Reviews , 2023 pp 105323
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"... 3.2 Effects on visual disorders 3.2.1 Alzheimer’s disease The effects of acetylcholine on visual plasticity and function can be further characterized in people with cognitive and visual disorders. Acetylcholinesterase inhibitors are clinically indicated for improving cognition in Alzheimer’s disease , and studies suggest that they may facilitate improved central visual processing as well. Physostigmine improves performance on a complex visual judgement task requiring patients with Alzheimer’s disease to determine the color and age of faces and buildings . Treatment with physostigmine selectively increases extrastriate cortex activity during the most difficult trials . Similar to its effects in healthy adults, acetylcholine has the greatest benefit for Alzheimer’s patients during challenging conditions. The therapeutic effect of acetylcholinesterase inhibitors on memory loss in Alzheimer’s disease extends to visual memory as well. Eight weeks of donepezil treatment in patients with mild-to-moderate cognitive impairment improves word learning and recall compared to placebo . Resting state metabolism in the prefrontal cortex and hippocampus, which influence attention and memory, increase with donepezil therapy . Interestingly, donepezil affects sensory integration as well. Audiovisual-evoked activity increases in the primary visual and auditory cortices, secondary visual and auditory cortices, and the posterior parietal cortex following treatment . Similarly, in an open-label study of ten patients with Alzheimer’s disease, ten weeks of donepezil therapy increases fusiform gyrus activity during a facial recognition task . Although cholinergic treatment had no effect on face recognition, it is unclear whether donepezil mitigates disease progression as performance did not significantly decrease over time and there was no placebo-controlled group . Acetylcholinesterase inhibitors may facilitate central visual processing in Alzheimer’s disease. 3.2.2 Amblyopia Several clinical trials have investigated the effects of citicoline on amblyopia and glaucoma. Amblyopia occurs when early untreated vision loss, often in one eye, causes a chronic decrease in visual acuity due to improper visual neural pathway development. 3 ..."
Reference 39
Reference works Chapter
Area V2
Daniel J. Felleman
Encyclopedia of the Human Brain , 2002 pp 199-222
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"... Visual Learning and Imagery It has been hypothesized that cortical areas involved in visual perception are also involved in the recall of images. This hypothesis has been tested using both fMRI and PET. In one study, subjects alternately viewed LED displays of flashing squares or were asked to imagine the display pattern. A region of high activity during the stimulation condition was observed in the posterior occipital cortex that was reported to include both areas V1 and V2. This same region showed strong, yet weaker activation during the imagine condition in five of the seven subjects tested. These results suggest that areas V1 and V2 are involved in the recall or imagination of visual stimuli. A second study reached a different conclusion using a different paradigm that allowed the assessment of the role of various cortical regions in visual learning, recall, and recognition. Subjects were presented various colored geometric patterns and were tested for their learning of the pattern contents. PET imaging was used to assess the cortical regions involved in the learning phase as well as in the recall and recognition of these learned patterns. Due to the limited spatial resolution of the PET method and the lack of topographic mapping in these experiments, it was not possible to assign activation foci to specific cortical areas. However, it was possible to compare the activations across learning, recall, and recognition conditions. Early cortical area V1 and adjacent pericalcarine areas (such as V2) were activated in the learning phase of this experiment. In contrast, no cortical regions in the occipital lobe were activated significantly during the recall of learned patterns. In addition, V1 and adjacent pericalcarine fields were activated during the recognition task, where learned patterns were presented intermixed with similar novel patterns. These results suggest that areas V1 and V2 are not involved in visual recall, but instead higher cortical and limbic areas are involved in this complex process. The differences in the results between this study and the first study appear substantial and may be attributable to methodological differences. 3 ..."
Reference 40
Review article
A Neural Chronometry of Memory Recall
Staresina B.P., Wimber M.
Trends in Cognitive Sciences , 2019 pp 1071-1085
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"... Critically, in this time window the neural signatures of memory reinstatement fluctuated rhythmically, waxing and waning at a theta frequency of 8 Hz ( Figure 3 B, bottom left). The decodability of perceived versus recalled objects was maximal at opposite phases of the theta cycle ( Figure 2 B, upper middle), consistent with computational models that predict a phase separation of information flowing into the hippocampus during encoding and out of the hippocampus during retrieval . This work allows the intriguing possibility that, between those theta states that are optimal for encoding and retrieval, respectively, a transition phase exists that provides the optimal time point for the perception-to-memory flip discussed in the previous section. Related to the critical time point of this reversal, the same study also suggests an interesting temporal relationship between theta phase and neocortical reinstatement. Time points of maximal memory reactivation were preceded by a theta phase-locked signal by approximately 250 ms ( Figure 3 B, bottom right). The delay is indicative of an upstream region (e.g., hippocampus) initiating the recall process at the optimal retrieval phase of the theta cycle followed by neocortical reactivation of mnemonic content 200–300 ms later, an interpretation corroborated by source analysis ( Figure 3 B, bottom right). This observation is of interest because human iEEG work points to a similar offset between the processing of a memory cue and hippocampal recall processes. For instance, one study recorded field potentials in the hippocampus and anterior temporal lobe (ATL) while participants encoded and later recalled cross-category associations . The directionality of oscillatory coupling between these regions changed during recall relative to encoding, with ATL engagement following a hippocampal recall signal with a delay of ∼250 ms. A study using single-neuron recordings examined the delay between visually selective (VS) and memory-selective (MS) MTL neurons during recognition and found that VS neurons responded approximately 200 ms earlier (from ∼250 ms) than MS neurons (from ∼450 ms). 4 ..."
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"... The Temporal Codes of Memory Recall As reviewed above, accumulating evidence suggests that hippocampal–neocortical dynamics between 500 and 1500 ms after a reminder reinstate mnemonic patterns. In this section, we zoom in on the temporal dynamics that govern the reinstatement process in this critical time window. We first review the evidence regarding the timeline of memory reactivation for single events and event sequences, before turning to the role of theta oscillations in clocking the reinstatement process. An Information Flow Reversal between Perception and Memory? During cued recall, sensory information pertaining to the cue enters the hippocampus in a feedforward fashion. When successfully matched with an overlapping, stored memory trace, hippocampal pattern completion then reinstates mnemonic target content back in neocortex (see computational models discussed in sections above ). The cue-to-memory conversion should thus be associated with a reversal of the information flow from a feedforward, cue-driven input process to a feedback, memory-driven output process. In experimental terms, study designs that use cross-category cued recall (e.g., object–scene or word–face associations) are particularly well suited for isolating purely mnemonic target reinstatement from perceptual cue processing. One fMRI study used cross-category (object–scene) cued recall in conjunction with dynamic causal modelling (DCM) to provide empirical support for the hypothesised reversal of information flow from cue to target. The same MTL cortical region was found either to send information to the hippocampus when its preferred category (objects for perirhinal cortex, scenes for parahippocampal cortex) served as the cue or to receive information from the hippocampus when its preferred category was the target . Similar results were obtained from studies employing laminar recordings in monkeys [53–55] . Using object-based cued recall, a feedforward signal was observed across perirhinal cortex layers during the cue period. 4 ..."
Reference 41
Reference works Chapter
Systems Neuroscience
Nathan S. Rose, Justine Fragetta, Robert M.G. Reinhart
Learning and Memory: A Comprehensive Reference , 2025 pp 389-412
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"... Photobiomodulation Photobiomodulation (PBM), also known as low level laser therapy is a form of NIBS that uses lasers (or LED lights) to stimulate cellular processes. PBM has been primarily used for tissue repair and pain relief and has recently gained attention for its applications in memory research. The metabolic effects following PBM can increase cerebral metabolic energy production, oxygen consumption, and blood flow in animals and humans . It has also been suggested that PBM can increase ATP production, enhance neuroprotection and neurogenesis, modulate neurotransmitters, and provide anti-inflammatory effects . AD is characterized by the accumulation of amyloid-beta (Aβ) plaques and neurofibrillary tangles (NFTs) in the brain, which is associated with cognitive deficits. Tao et al. (2021) administered PBM to an AD mouse model and found that 1070-nm light reduced the cerebral Aβ burden and mitigated recognition memory impairment. Chan et al. (2021) investigated the effects of PBM on memory in a sample of older adults with mild cognitive impairment (MCI). Individuals who received active PBM showed significant improvements on a visual memory task, which were accompanied by reduced hemodynamic responses (measured by functional near-infrared spectroscopy) in prefrontal cortex, as compared to a sham stimulation group. Based on these results, the authors suggested that PBM may lessen cognitive effort in tasks requiring high memory loads, potentially improving cognitive performance in individuals with MCI. In a sample of healthy older adults, Qu et al. (2022) studied the effects of repeated PBM on WM as compared to single sessions. They found that both repeated (7 days) and single PBM sessions significantly enhanced accuracy rates and reduced response times on a WM task, with repeated sessions showing greater improvements. These benefits persisted for at least 3 weeks post-intervention, suggesting potential as an intervention for memory decline in older individuals. 4 ..."
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"... Noninvasive brain stimulation (NIBS) Currently, the two most popular noninvasive brain stimulation (NIBS) techniques are transcranial magnetic stimulation (TMS) and transcranial electric stimulation (tES). Additionally, transcranial focused ultrasound stimulation (tFUS) and transcranial photobiomodulation are two relatively new and promising techniques for modulating metabolic processes in the brain that support memory functioning. Each of these techniques can be used to modulate neuronal activity with varying degrees of spatial specificity, and can have an inhibitory or facilitatory effect on more widespread brain and behavioral functioning. TMS uses rapidly changing electromagnetic fields to stimulate the underlying cortical surface, while tES involves the application of a weak electrical current. These differ from photobiomodulation and tFUS, which use light illumination and ultrasound waves to modulate neural activity, respectively. The cognitive effects produced by TMS and TES depend on the propagation of the induced electromagnetic field, which is influenced by both external methodological factors (e.g. technical parameters used during stimulation) and internal factors such as individual cortical geometry and attentional and physiological states . The electric field alters neuronal excitability by modulating the activity of ion channels and altering the transmembrane potential. While NIBS can be used to temporarily and reversibly modulate memory performance, long-lasting effects are also observed following stimulation. Just as with endogenous brain activity following sensory and cognitive “stimulation,” and exogenous stimulation caused by invasive methods, LTP and LTD are, at the synaptic level, the physiological mechanisms responsible for the changes observed following NIBS . As introduced above in the opening section on memory, the terms LTP and LTD refer to the collection of cellular mechanisms through which synaptic connections are modified in response to activity patterns. These forms of synaptic plasticity represent the core mechanisms involved in learning and memory processes. 4 ..."

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