Reconstructing representations of dynamic visual objects in early visual cortex

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.

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The Neural Codes Underlying Internally Generated Representations in Visual Working Memory

Journal of Cognitive Neuroscience ◽

10.1162/jocn_a_01702 ◽

2021 ◽

pp. 1-16

Author(s):

Qing Yu ◽

Bradley R. Postle

Keyword(s):

Working Memory ◽

Visual Cortex ◽

Visual Working Memory ◽

Subjective Experience ◽

Neural Representation ◽

Delayed Recall ◽

Early Visual Cortex ◽

Memory Representations ◽

Internal Sources ◽

Scaling Analyses

Abstract Humans can construct rich subjective experience even when no information is available in the external world. Here, we investigated the neural representation of purely internally generated stimulus-like information during visual working memory. Participants performed delayed recall of oriented gratings embedded in noise with varying contrast during fMRI scanning. Their trialwise behavioral responses provided an estimate of their mental representation of the to-be-reported orientation. We used multivariate inverted encoding models to reconstruct the neural representations of orientation in reference to the response. We found that response orientation could be successfully reconstructed from activity in early visual cortex, even on 0% contrast trials when no orientation information was actually presented, suggesting the existence of a purely internally generated neural code in early visual cortex. In addition, cross-generalization and multidimensional scaling analyses demonstrated that information derived from internal sources was represented differently from typical working memory representations, which receive influences from both external and internal sources. Similar results were also observed in intraparietal sulcus, with slightly different cross-generalization patterns. These results suggest a potential mechanism for how externally driven and internally generated information is maintained in working memory.

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Defining the Units of Competition: Influences of Perceptual Organization on Competitive Interactions in Human Visual Cortex

Journal of Cognitive Neuroscience ◽

10.1162/jocn.2009.21391 ◽

2010 ◽

Vol 22 (11) ◽

pp. 2417-2426 ◽

Cited By ~ 27

Author(s):

Stephanie A. McMains ◽

Sabine Kastner

Keyword(s):

Visual Cortex ◽

Perceptual Organization ◽

Visual Processing ◽

Perceptual Grouping ◽

Neural Representation ◽

Competitive Interactions ◽

Illusory Figure ◽

Processing Stream ◽

Neural Processes ◽

Early Visual Cortex

Multiple stimuli that are present simultaneously in the visual field compete for neural representation. At the same time, however, multiple stimuli in cluttered scenes also undergo perceptual organization according to certain rules originally defined by the Gestalt psychologists such as similarity or proximity, thereby segmenting scenes into candidate objects. How can these two seemingly orthogonal neural processes that occur early in the visual processing stream be reconciled? One possibility is that competition occurs among perceptual groups rather than at the level of elements within a group. We probed this idea using fMRI by assessing competitive interactions across visual cortex in displays containing varying degrees of perceptual organization or perceptual grouping (Grp). In strong Grp displays, elements were arranged such that either an illusory figure or a group of collinear elements were present, whereas in weak Grp displays the same elements were arranged randomly. Competitive interactions among stimuli were overcome throughout early visual cortex and V4, when elements were grouped regardless of Grp type. Our findings suggest that context-dependent grouping mechanisms and competitive interactions are linked to provide a bottom–up bias toward candidate objects in cluttered scenes.

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

eLife ◽

10.7554/elife.27819 ◽

2017 ◽

Vol 6 ◽

Cited By ~ 4

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.

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Probabilistic representation in human visual cortex reflects uncertainty in serial decisions

10.1101/671958 ◽

2019 ◽

Author(s):

R.S. van Bergen ◽

J.F.M. Jehee

Keyword(s):

Visual Cortex ◽

Neural Coding ◽

Probability Distributions ◽

Sensory Information ◽

Population Level ◽

Neural Representation ◽

Serial Dependence ◽

Population Activity ◽

Human Visual Cortex ◽

Sensory Uncertainty

AbstractHow does the brain represent the reliability of its sensory evidence? Here, we test whether sensory uncertainty is encoded in cortical population activity as the width of a probability distribution – a hypothesis that lies at the heart of Bayesian models of neural coding. We probe the neural representation of uncertainty by capitalizing on a well-known behavioral bias called serial dependence. Human observers of either sex reported the orientation of stimuli presented in sequence, while activity in visual cortex was measured with fMRI. We decoded probability distributions from population-level activity and found that serial dependence effects in behavior are consistent with a statistically advantageous sensory integration strategy, in which uncertain sensory information is given less weight. More fundamentally, our results suggest that probability distributions decoded from human visual cortex reflect the sensory uncertainty that observers rely on in their decisions, providing critical evidence for Bayesian theories of perception.

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The geometry of masking in neural populations

Nature Communications ◽

10.1038/s41467-019-12881-4 ◽

2019 ◽

Vol 10 (1) ◽

Cited By ~ 1

Author(s):

Dario L. Ringach

Keyword(s):

Visual Cortex ◽

Cortical Neurons ◽

Dimensional Space ◽

Geometric Analysis ◽

Geometric Approach ◽

Population Level ◽

Contextual Modulation ◽

Neural Populations ◽

Early Visual Cortex ◽

Low Dimensional

Abstract The normalization model provides an elegant account of contextual modulation in individual neurons of primary visual cortex. Understanding the implications of normalization at the population level is hindered by the heterogeneity of cortical neurons, which differ in the composition of their normalization pools and semi-saturation constants. Here we introduce a geometric approach to investigate contextual modulation in neural populations and study how the representation of stimulus orientation is transformed by the presence of a mask. We find that population responses can be embedded in a low-dimensional space and that an affine transform can account for the effects of masking. The geometric analysis further reveals a link between changes in discriminability and bias induced by the mask. We propose the geometric approach can yield new insights into the image processing computations taking place in early visual cortex at the population level while coping with the heterogeneity of single cell behavior.

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Action intention modulates the representation of object features in early visual cortex

10.1101/480574 ◽

2018 ◽

Author(s):

Jena Velji-Ibrahim ◽

J. Douglas Crawford ◽

Luigi Cattaneo ◽

Simona Monaco

Keyword(s):

Visual Cortex ◽

Functional Connectivity ◽

Interaction Analysis ◽

Action Planning ◽

Hand Movements ◽

Dominant Hand ◽

Hand Orientation ◽

Early Visual Cortex ◽

Object Features ◽

Decoding Accuracy

AbstractThe role of the early visual cortex (EVC) has been extensively studied for visual recognition but to a lesser degree to determine how action planning influences perceptual representations of objects. We used functional MRI and pattern classification methods to determine if during action planning, object features (orientation and location) could be decoded in an action-dependent way and if so, whether this was due to functional connectivity between visual and higher-level cortical areas. Sixteen participants used their right dominant hand to perform movements (Align or Open Hand) towards one of two oriented objects that were simultaneously presented and placed on either side of a fixation cross. While both movements required aiming toward target location, only Align movements required participants to precisely adjust hand orientation. Therefore, we hypothesized that if the representation of object features in the EVC is modulated by the upcoming action, we could use the pre-movement activity pattern to dissociate between object locations in both tasks, and orientations in the Align task only. We found above chance decoding accuracy between the two objects for both tasks in the calcarine sulcus corresponding to the peripheral location of the objects in the visual cortex, suggesting a task-independent (i.e. location) modulation. In contrast, we found significant decoding accuracy between the two objects for Align but not Open Hand movements in the occipital pole corresponding to central vision, and dorsal stream areas, suggesting a task-dependent (i.e. orientation) modulation. Psychophysiological interaction analysis indicated stronger functional connectivity during the planning phase of Align than Open Hand movements between EVC and sensory-motor areas in the dorsal and ventral visual stream, as well as areas that lie at the interface between the two streams. These results demonstrate that task-specific preparatory signals modulate activity not only in areas typically known to be involved in perception for action, but also in the EVC. Further, our findings suggest that object features that are relevant for successful action performance are represented in the part of the visual cortex that is best suited to process visual features in great details, such as the foveal cortex, even if the objects are viewed in the periphery.

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

10.1101/456566 ◽

2018 ◽

Cited By ~ 2

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.

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

10.1101/124867 ◽

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.

Download Full-text