scholarly journals Increasing suppression of saccade-related transients along the human visual hierarchy

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Tal Golan ◽  
Ido Davidesco ◽  
Meir Meshulam ◽  
David M Groppe ◽  
Pierre Mégevand ◽  
...  
Keyword(s):  
Visual Cortex ◽  
High Frequency ◽  
Large Individual ◽  
Perceptual Awareness ◽  
Eye Blinks ◽  
Visual Objects ◽  
Visual Hierarchy ◽  
Neurosurgical Patients ◽  
Early Visual Cortex ◽  
High Frequency Activity

A key hallmark of visual perceptual awareness is robustness to instabilities arising from unnoticeable eye and eyelid movements. In previous human intracranial (iEEG) work (Golan et al., 2016) we found that excitatory broadband high-frequency activity transients, driven by eye blinks, are suppressed in higher-level but not early visual cortex. Here, we utilized the broad anatomical coverage of iEEG recordings in 12 eye-tracked neurosurgical patients to test whether a similar stabilizing mechanism operates following small saccades. We compared saccades (1.3°−3.7°) initiated during inspection of large individual visual objects with similarly-sized external stimulus displacements. Early visual cortex sites responded with positive transients to both conditions. In contrast, in both dorsal and ventral higher-level sites the response to saccades (but not to external displacements) was suppressed. These findings indicate that early visual cortex is highly unstable compared to higher-level visual regions which apparently constitute the main target of stabilizing extra-retinal oculomotor influences.

scholarly journals Increasing suppression of saccade-related transients along the human visual hierarchy

2017 ◽  
Author(s):  
Tal Golan ◽  
Ido Davidesco ◽  
Meir Meshulam ◽  
David M Groppe ◽  
Pierre Mégevand ◽  
...  
Keyword(s):  
Visual Cortex ◽  
High Frequency ◽  
Large Individual ◽  
Perceptual Awareness ◽  
Eye Blinks ◽  
Visual Objects ◽  
Visual Hierarchy ◽  
Neurosurgical Patients ◽  
Early Visual Cortex ◽  
High Frequency Activity

AbstractA key hallmark of visual perceptual awareness is robustness to instabilities arising from unnoticeable eye and eyelid movements. In previous human intracranial (iEEG) work (Golan et al., 2016) we found that excitatory broadband high-frequency activity transients, driven by eye blinks, are suppressed in higher-level but not early visual cortex. Here, we utilized the broad anatomical coverage of iEEG recordings in 12 eye-tracked neurosurgical patients to test whether a similar stabilizing mechanism operates following small saccades. We compared saccades (1.3°-3.7°) initiated during inspection of large individual visual objects with similarly-sized external stimulus displacements. Early visual cortex sites responded with positive transients to both conditions. In contrast, in both dorsal and ventral higher-level sites the response to saccades (but not to external displacements) was suppressed. These findings indicate that early visual cortex is highly unstable compared to higher-level visual regions which apparently constitute the main target of stabilizing extra-retinal oculomotor influences.

scholarly journals Concurrent feature-specific reactivation within the hippocampus and neocortex facilitates episodic memory retrieval

2021 ◽  
Author(s):  
Michael B. Bone ◽  
Bradley R. Buchsbaum
Keyword(s):  
Visual Cortex ◽  
Memory Retrieval ◽  
Visual Memory ◽  
Recognition Accuracy ◽  
Memory Task ◽  
Large Individual ◽  
Storage And Retrieval ◽  
Specific Index ◽  
Early Visual Cortex ◽  
Episodic Memories

AbstractThe hippocampus is a key brain region for the storage and retrieval of episodic memories, but how it performs this function is unresolved. According to the hippocampal indexing theory, the hippocampus stores an event-specific index of the pattern of neocortical activity that occurred during perception. During retrieval, reactivation of the index by a partial cue facilitates the reactivation of the associated neocortical pattern. Therefore, event-specific retrieval requires joint reactivation of the hippocampal index and the associated neocortical networks. To test this theory, we examine the relation between performance on a recognition memory task requiring retrieval of image-specific visual details and feature-specific reactivation within the hippocampus and neocortex. We show that trial-by-trial recognition accuracy correlates with neural reactivation of low-level features (e.g. luminosity and edges) within the posterior hippocampus and early visual cortex for participants with high recognition lure accuracy. As predicted, the two regions interact, such that recognition accuracy correlates with hippocampal reactivation only when reactivation co-occurs within the early visual cortex (and vice-versa). In addition to supporting the hippocampal indexing theory, our findings show large individual differences in the features underlying visual memory and suggest that the anterior and posterior hippocampus represents gist-like and detailed features, respectively.

scholarly journals Human intracranial recordings link suppressed transients rather than 'filling-in' to perceptual continuity across blinks

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Tal Golan ◽  
Ido Davidesco ◽  
Meir Meshulam ◽  
David M Groppe ◽  
Pierre Mégevand ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Neural Correlates ◽  
Activity Level ◽  
Human Visual Cortex ◽  
Eye Blinks ◽  
Visual Activity ◽  
Visual Hierarchy ◽  
Video Frames ◽  
Visual Areas ◽  
Intracranial Recordings

We hardly notice our eye blinks, yet an externally generated retinal interruption of a similar duration is perceptually salient. We examined the neural correlates of this perceptual distinction using intracranially measured ECoG signals from the human visual cortex in 14 patients. In early visual areas (V1 and V2), the disappearance of the stimulus due to either invisible blinks or salient blank video frames ('gaps') led to a similar drop in activity level, followed by a positive overshoot beyond baseline, triggered by stimulus reappearance. Ascending the visual hierarchy, the reappearance-related overshoot gradually subsided for blinks but not for gaps. By contrast, the disappearance-related drop did not follow the perceptual distinction – it was actually slightly more pronounced for blinks than for gaps. These findings suggest that blinks' limited visibility compared with gaps is correlated with suppression of blink-related visual activity transients, rather than with "filling-in" of the occluded content during blinks.

scholarly journals Widespread Suppression of High-Order Visual Cortex During Blinks and External Predictable Visual Interruptions

2018 ◽  
Author(s):  
Tal Golan ◽  
Shany Grossman ◽  
Leon Y Deouell ◽  
Rafael Malach
Keyword(s):  
Visual Cortex ◽  
Visual Awareness ◽  
General Purpose ◽  
High Order ◽  
Still Images ◽  
Visual Hierarchy ◽  
Retinal Input ◽  
Early Visual Cortex ◽  
High Level

AbstractSpontaneous eye blinks generate frequent potent interruptions to the retinal input and yet go unnoticed. As such, they provide an attractive approach to the study of the neural correlates of visual awareness. Here, we tested the potential role of predictability in generating blink-related effects using fMRI. While participants attentively watched still images of faces and houses, we monitored naturally occurring spontaneous blinks and introduced three kinds of matched visual interruptions: cued voluntary blinks, self-initiated (and hence, predictable) external darkenings, and physically similar but unpredictable external darkenings. These events’ impact was inspected using fMRI across the visual hierarchy. In early visual cortex, both spontaneous and voluntary blinks, as well as predictable and unpredictable external darkenings, led to largely similar positive responses in peripheral representations. In mid- and high-level visual cortex, all predictable conditions (spontaneous blinks, voluntary blinks, and self-initiated external darkenings) were associated with signal decreases. In contrast, unpredictable darkenings were associated with signal increases. These findings suggest that general-purpose prediction-related mechanisms are involved in producing a small but widespread suppression of mid- and high-order visual regions during blinks. Such suppression may down-regulate responses to predictable transients in the human visual hierarchy.

scholarly journals Reconstructing representations of dynamic visual objects in early visual cortex

2015 ◽  
Vol 113 (5) ◽  
pp. 1453-1458 ◽  
Author(s):  
Edmund Chong ◽  
Ariana M. Familiar ◽  
Won Mok Shim
Keyword(s):  
Visual Cortex ◽  
Population Level ◽  
Neural Representation ◽  
Test Case ◽  
Missing Information ◽  
Sensory Data ◽  
Visual Objects ◽  
Retinal Input ◽  
Early Visual Cortex ◽  
Object Features

As raw sensory data are partial, our visual system extensively fills in missing details, creating enriched percepts based on incomplete bottom-up information. Despite evidence for internally generated representations at early stages of cortical processing, it is not known whether these representations include missing information of dynamically transforming objects. Long-range apparent motion (AM) provides a unique test case because objects in AM can undergo changes both in position and in features. Using fMRI and encoding methods, we found that the “intermediate” orientation of an apparently rotating grating, never presented in the retinal input but interpolated during AM, is reconstructed in population-level, feature-selective tuning responses in the region of early visual cortex (V1) that corresponds to the retinotopic location of the AM path. This neural representation is absent when AM inducers are presented simultaneously and when AM is visually imagined. Our results demonstrate dynamic filling-in in V1 for object features that are interpolated during kinetic transformations.

Basic Level Category Structure Emerges Gradually across Human Ventral Visual Cortex

2015 ◽  
Vol 27 (7) ◽  
pp. 1427-1446 ◽  
Author(s):  
Marius Cătălin Iordan ◽  
Michelle R. Greene ◽  
Diane M. Beck ◽  
Li Fei-Fei
Keyword(s):  
Visual Cortex ◽  
Activity Patterns ◽  
Object Categories ◽  
Visual Hierarchy ◽  
Subordinate Level ◽  
Early Visual Cortex ◽  
Occipitotemporal Cortex ◽  
Feature Overlap ◽  
The Brain ◽  
Basic Level

Objects can be simultaneously categorized at multiple levels of specificity ranging from very broad (“natural object”) to very distinct (“Mr. Woof”), with a mid-level of generality (basic level: “dog”) often providing the most cognitively useful distinction between categories. It is unknown, however, how this hierarchical representation is achieved in the brain. Using multivoxel pattern analyses, we examined how well each taxonomic level (superordinate, basic, and subordinate) of real-world object categories is represented across occipitotemporal cortex. We found that, although in early visual cortex objects are best represented at the subordinate level (an effect mostly driven by low-level feature overlap between objects in the same category), this advantage diminishes compared to the basic level as we move up the visual hierarchy, disappearing in object-selective regions of occipitotemporal cortex. This pattern stems from a combined increase in within-category similarity (category cohesion) and between-category dissimilarity (category distinctiveness) of neural activity patterns at the basic level, relative to both subordinate and superordinate levels, suggesting that successive visual areas may be optimizing basic level representations.

scholarly journals How do the blind ‘see’? The role of spontaneous brain activity in self-generated perception

Brain ◽  
2020 ◽  
Author(s):  
Avital Hahamy ◽  
Meytal Wilf ◽  
Boris Rosin ◽  
Marlene Behrmann ◽  
Rafael Malach
Keyword(s):  
Visual Cortex ◽  
Visual System ◽  
Brain Activity ◽  
Visual Hallucinations ◽  
Charles Bonnet Syndrome ◽  
Spontaneous Brain Activity ◽  
Visual Hierarchy ◽  
Early Visual Cortex ◽  
Spontaneous Fluctuations

Abstract Spontaneous activity of the human brain has been well documented, but little is known about the functional role of this ubiquitous neural phenomenon. It has previously been hypothesized that spontaneous brain activity underlies unprompted (internally generated) behaviour. We tested whether spontaneous brain activity might underlie internally-generated vision by studying the cortical visual system of five blind/visually-impaired individuals who experience vivid visual hallucinations (Charles Bonnet syndrome). Neural populations in the visual system of these individuals are deprived of external input, which may lead to their hyper-sensitization to spontaneous activity fluctuations. To test whether these spontaneous fluctuations can subserve visual hallucinations, the functional MRI brain activity of participants with Charles Bonnet syndrome obtained while they reported their hallucinations (spontaneous internally-generated vision) was compared to the: (i) brain activity evoked by veridical vision (externally-triggered vision) in sighted controls who were presented with a visual simulation of the hallucinatory streams; and (ii) brain activity of non-hallucinating blind controls during visual imagery (cued internally-generated vision). All conditions showed activity spanning large portions of the visual system. However, only the hallucination condition in the Charles Bonnet syndrome participants demonstrated unique temporal dynamics, characterized by a slow build-up of neural activity prior to the reported onset of hallucinations. This build-up was most pronounced in early visual cortex and then decayed along the visual hierarchy. These results suggest that, in the absence of external visual input, a build-up of spontaneous fluctuations in early visual cortex may activate the visual hierarchy, thereby triggering the experience of vision.

scholarly journals Representation of contralateral visual space in the human hippocampus

2020 ◽  
Author(s):  
Edward H Silson ◽  
Peter Zeidman ◽  
Tomas Knapen ◽  
Chris I Baker
Keyword(s):  
Visual Cortex ◽  
Visual Field ◽  
Receptive Field ◽  
Visual Information ◽  
Visual Space ◽  
Spatial Representations ◽  
Visual Hierarchy ◽  
Human Hippocampus ◽  
Human Connectome Project ◽  
Early Visual Cortex

AbstractThe initial encoding of visual information primarily from the contralateral visual field is a fundamental organizing principle of the primate visual system. Recently, the presence of such retinotopic sensitivity has been shown to extend well beyond early visual cortex to regions not historically considered retinotopically sensitive. In particular, human scene-selective regions in parahippocampal and medial parietal cortex exhibit prominent biases for the contralateral visual field. Here we used fMRI to test the hypothesis that the human hippocampus, which is thought to be anatomically connected with these scene-selective regions, would also exhibit a biased representation of contralateral visual space. First, population receptive field mapping with scene stimuli revealed strong biases for the contralateral visual field in bilateral hippocampus. Second, the distribution of retinotopic sensitivity suggested a more prominent representation in anterior medial portions of the hippocampus. Finally, the contralateral bias was confirmed in independent data taken from the Human Connectome Project initiative. The presence of contralateral biases in the hippocampus – a structure considered by many as the apex of the visual hierarchy - highlights the truly pervasive influence of retinotopy. Moreover, this finding has important implications for understanding how this information relates to the allocentric global spatial representations known to be encoded therein.Significance StatementRetinotopic encoding of visual information is an organizing principle of visual cortex. Recent work demonstrates this sensitivity in structures far beyond early visual cortex, including those anatomically connected to the hippocampus. Here, using population receptive field modelling in two independent sets of data we demonstrate a consistent bias for the contralateral visual field in bilateral hippocampus. Such a bias highlights the truly pervasive influence of retinotopy, with important implications for understanding how the presence of retinotopy relates to more allocentric spatial representations.

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