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 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 A TMS-EROS investigation of the role of feedback to early visual cortex in visual awareness.

2019 ◽  
Vol 19 (10) ◽  
pp. 169a
Author(s):  
Ramisha Knight ◽  
Gabriele Gratton ◽  
Monica Fabiani ◽  
Diane M Beck
Keyword(s):  
Visual Cortex ◽  
Visual Awareness ◽  
Early Visual Cortex

scholarly journals Visual Awareness Is Limited by the Representational Architecture of the Visual System

2015 ◽  
Vol 27 (11) ◽  
pp. 2240-2252 ◽  
Author(s):  
Michael A. Cohen ◽  
Ken Nakayama ◽  
Talia Konkle ◽  
Mirta Stantić ◽  
George A. Alvarez
Keyword(s):  
Visual Cortex ◽  
Visual System ◽  
Visual Masking ◽  
Visual Awareness ◽  
Neural Responses ◽  
Dorsal Pathway ◽  
Visual Hierarchy ◽  
Early Visual Cortex ◽  
Ventral Pathway ◽  
Brain Behavior

Visual perception and awareness have strict limitations. We suggest that one source of these limitations is the representational architecture of the visual system. Under this view, the extent to which items activate the same neural channels constrains the amount of information that can be processed by the visual system and ultimately reach awareness. Here, we measured how well stimuli from different categories (e.g., faces and cars) blocked one another from reaching awareness using two distinct paradigms that render stimuli invisible: visual masking and continuous flash suppression. Next, we used fMRI to measure the similarity of the neural responses elicited by these categories across the entire visual hierarchy. Overall, we found strong brain–behavior correlations within the ventral pathway, weaker correlations in the dorsal pathway, and no correlations in early visual cortex (V1–V3). These results suggest that the organization of higher level visual cortex constrains visual awareness and the overall processing capacity of visual cognition.

scholarly journals Neural Correlates of Motion-induced Blindness in the Human Brain

2010 ◽  
Vol 22 (6) ◽  
pp. 1235-1243 ◽  
Author(s):  
Marieke L. Schölvinck ◽  
Geraint Rees
Keyword(s):  
Visual Cortex ◽  
Visual Processing ◽  
Target Location ◽  
Visual Awareness ◽  
Neural Correlates ◽  
Low Level ◽  
Bistable Perception ◽  
Visual Phenomenon ◽  
High Level ◽  
Visual Cortical

Motion-induced blindness (MIB) is a visual phenomenon in which highly salient visual targets spontaneously disappear from visual awareness (and subsequently reappear) when superimposed on a moving background of distracters. Such fluctuations in awareness of the targets, although they remain physically present, provide an ideal paradigm to study the neural correlates of visual awareness. Existing behavioral data on MIB are consistent both with a role for structures early in visual processing and with involvement of high-level visual processes. To further investigate this issue, we used high field functional MRI to investigate signals in human low-level visual cortex and motion-sensitive area V5/MT while participants reported disappearance and reappearance of an MIB target. Surprisingly, perceptual invisibility of the target was coupled to an increase in activity in low-level visual cortex plus area V5/MT compared with when the target was visible. This increase was largest in retinotopic regions representing the target location. One possibility is that our findings result from an active process of completion of the field of distracters that acts locally in the visual cortex, coupled to a more global process that facilitates invisibility in general visual cortex. Our findings show that the earliest anatomical stages of human visual cortical processing are implicated in MIB, as with other forms of bistable perception.

Unconscious inference and conscious representation: Why primary visual cortex (V1) is directly involved in visual awareness

2008 ◽  
Vol 31 (2) ◽  
pp. 209-210 ◽  
Author(s):  
Zhicheng Lin
Keyword(s):  
Visual Cortex ◽  
Primary Visual Cortex ◽  
Visual Processing ◽  
Vision System ◽  
Visual Awareness ◽  
Moving Object ◽  
Delay Compensation ◽  
Visual Hierarchy ◽  
Target Article ◽  
Visual Delay

AbstractThe extent to which visual processing can proceed in the visual hierarchy without awareness determines the magnitude of perceptual delay. Increasing data demonstrate that primary visual cortex (V1) is involved in consciousness, constraining the magnitude of visual delay. This makes it possible that visual delay is actually within the optimal lengths to allow sufficient computation; thus it might be unnecessary to compensate for visual delay.The time delay problem – that perception lives slightly in the past as a result of neural conduction – has recently attracted a considerate amount of attention in the context of the flash-lag effect. The effect refers to a visual illusion wherein a brief flash of light and a continuously moving object that physically align in space and time are perceived to be displaced from one another – the flashed stimulus appears to lag behind the moving object (Krekelberg & Lappe 2001). In the target article, Nijhawan compellingly argues that delay compensation could be undertaken by a predictive process in the feedforward pathways in the vision system. Before jumping into the quest for the mechanism of delay compensation, however, I would like to argue that the magnitude of delay has been overestimated, and that it might even be unnecessary to compensate for such a delay.

Determinants of motion response anisotropies in human early visual cortex: The role of configuration and eccentricity

NeuroImage ◽  
2014 ◽  
Vol 100 ◽  
pp. 564-579 ◽  
Author(s):  
Ryan T. Maloney ◽  
Tamara L. Watson ◽  
Colin W.G. Clifford
Keyword(s):  
Visual Cortex ◽  
Motion Response ◽  
Early Visual Cortex

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 Feedback contribution to surface motion perception in the human early visual cortex

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Ingo Marquardt ◽  
Peter De Weerd ◽  
Marian Schneider ◽  
Omer Faruk Gulban ◽  
Dimo Ivanov ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Motion Perception ◽  
Depth Distribution ◽  
Ultra High Field ◽  
Surface Perception ◽  
Surface Motion ◽  
Surface Segmentation ◽  
Early Visual Cortex ◽  
Illusory Perception

Human visual surface perception has neural correlates in early visual cortex, but the role of feedback during surface segmentation in human early visual cortex remains unknown. Feedback projections preferentially enter superficial and deep anatomical layers, which provides a hypothesis for the cortical depth distribution of fMRI activity related to feedback. Using ultra-high field fMRI, we report a depth distribution of activation in line with feedback during the (illusory) perception of surface motion. Our results fit with a signal re-entering in superficial depths of V1, followed by a feedforward sweep of the re-entered information through V2 and V3. The magnitude and sign of the BOLD response strongly depended on the presence of texture in the background, and was additionally modulated by the presence of illusory motion perception compatible with feedback. In summary, the present study demonstrates the potential of depth-resolved fMRI in tackling biomechanical questions on perception.

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