Word contexts enhance the neural representation of individual letters in early visual cortex

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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Working memory representations in visual cortex mediate distraction effects

Nature Communications ◽

10.1038/s41467-021-24973-1 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Grace E. Hallenbeck ◽

Thomas C. Sprague ◽

Masih Rahmati ◽

Kartik K. Sreenivasan ◽

Clayton E. Curtis

Keyword(s):

Working Memory ◽

Visual Cortex ◽

Visual Memory ◽

Neural Representation ◽

Association Cortex ◽

Catastrophic Loss ◽

Visual Tasks ◽

Early Visual Cortex ◽

Memory Representations ◽

The Impact

AbstractAlthough the contents of working memory can be decoded from visual cortex activity, these representations may play a limited role if they are not robust to distraction. We used model-based fMRI to estimate the impact of distracting visual tasks on working memory representations in several visual field maps in visual and frontoparietal association cortex. Here, we show distraction causes the fidelity of working memory representations to briefly dip when both the memorandum and distractor are jointly encoded by the population activities. Distraction induces small biases in memory errors which can be predicted by biases in neural decoding in early visual cortex, but not other regions. Although distraction briefly disrupts working memory representations, the widespread redundancy with which working memory information is encoded may protect against catastrophic loss. In early visual cortex, the neural representation of information in working memory and behavioral performance are intertwined, solidifying its importance in visual memory.

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Reconstructing representations of dynamic visual objects in early visual cortex

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1512144113 ◽

2015 ◽

Vol 113 (5) ◽

pp. 1453-1458 ◽

Cited By ~ 22

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.

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Signals Related to Color in the Early Visual Cortex

Annual Review of Vision Science ◽

10.1146/annurev-vision-121219-081801 ◽

2020 ◽

Vol 6 (1) ◽

pp. 287-311 ◽

Cited By ~ 1

Author(s):

Gregory D. Horwitz

Keyword(s):

Visual Cortex ◽

Neural Representation ◽

Visual Images ◽

Natural Image ◽

Clear Understanding ◽

Natural Image Statistics ◽

Future Directions ◽

Neural Populations ◽

Early Visual Cortex ◽

Experimental Approaches

Visual images can be described in terms of the illuminants and objects that are causal to the light reaching the eye, the retinal image, its neural representation, or how the image is perceived. Respecting the differences among these distinct levels of description can be challenging but is crucial for a clear understanding of color vision. This article approaches color by reviewing what is known about its neural representation in the early visual cortex, with a brief description of signals in the eye and the thalamus for context. The review focuses on the properties of single neurons and advances the general theme that experimental approaches based on knowledge of feedforward signals have promoted greater understanding of the neural code for color than approaches based on correlating single-unit responses with color perception. New data from area V1 illustrate the strength of the feedforward approach. Future directions for progress in color neurophysiology are discussed: techniques for improved single-neuron characterization, for investigations of neural populations and small circuits, and for the analysis of natural image statistics.

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Neural Representation of Form-Based Color Filling-In in Early Visual Cortex

Journal of Vision ◽

10.1167/11.11.379 ◽

2011 ◽

Vol 11 (11) ◽

pp. 379-379

Author(s):

S. W. Hong ◽

F. Tong

Keyword(s):

Visual Cortex ◽

Neural Representation ◽

Early Visual Cortex

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Early Numerosity Encoding in Visual Cortex Is Not Sufficient for the Representation of Numerical Magnitude

Journal of Cognitive Neuroscience ◽

10.1162/jocn_a_01320 ◽

2018 ◽

Vol 30 (12) ◽

pp. 1788-1802 ◽

Cited By ~ 17

Author(s):

Michele Fornaciai ◽

Joonkoo Park

Keyword(s):

Visual Cortex ◽

Neural Activity ◽

Stimulus Onset ◽

Neural Representation ◽

Numerical Magnitude ◽

Sensory Representation ◽

Area V2 ◽

Early Visual Cortex ◽

Multivariate Pattern ◽

Number Perception

Recent studies have demonstrated that the numerosity of visually presented dot arrays is represented in low-level visual cortex extremely early in latency. However, whether or not such an early neural signature reflects the perceptual representation of numerosity remains unknown. Alternatively, such a signature may indicate the raw sensory representation of the dot-array stimulus before becoming the perceived representation of numerosity. Here, we addressed this question by using the connectedness illusion, whereby arrays with pairwise connected dots are perceived to be less numerous compared with arrays containing isolated dots. Using EEG and fMRI in two independent experiments, we measured neural responses to dot-array stimuli comprising 16 or 32 dots, either isolated or pairwise connected. The effect of connectedness, which reflects the segmentation of the visual stimulus into perceptual units, was observed in the neural activity after 150 msec post stimulus onset in the EEG experiment and in area V3 in the fMRI experiment using a multivariate pattern analysis. In contrast, earlier neural activity before 100 msec and in area V2 was strictly modulated by numerosity regardless of connectedness, suggesting that this early activity reflects the sensory representation of a dot array before perceptual segmentation. Our findings thus demonstrate that the neural representation for numerosity in early visual cortex is not sufficient for visual number perception and suggest that the perceptual encoding of numerosity occurs at or after the segmentation process that takes place later in area V3.

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A Varying Role for Abstraction in Models of Category Learning Constructed from Neural Representations in Early Visual Cortex

Journal of Cognitive Neuroscience ◽

10.1162/jocn_a_01339 ◽

2019 ◽

Vol 31 (1) ◽

pp. 155-173 ◽

Cited By ~ 5

Author(s):

J. Brendan Ritchie ◽

Hans Op de Beeck

Keyword(s):

Visual Cortex ◽

Category Learning ◽

Neural Representation ◽

Neural Responses ◽

Object Categories ◽

Neural Representations ◽

Learning Tasks ◽

Multiple Dimensions ◽

Wide Range ◽

Early Visual Cortex

The human capacity for visual categorization is core to how we make sense of the visible world. Although a substantive body of research in cognitive neuroscience has localized this capacity to regions of human visual cortex, relatively few studies have investigated the role of abstraction in how representations for novel object categories are constructed from the neural representation of stimulus dimensions. Using human fMRI coupled with formal modeling of observer behavior, we assess a wide range of categorization models that vary in their level of abstraction from collections of subprototypes to representations of individual exemplars. The category learning tasks range from simple linear and unidimensional category rules to complex crisscross rules that require a nonlinear combination of multiple dimensions. We show that models based on neural responses in primary visual cortex favor a variable, but often limited, extent of abstraction in the construction of representations for novel categories, which differ in degree across tasks and individuals.

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Different states of priority recruit different neural codes in visual working memory

10.1101/334920 ◽

2018 ◽

Cited By ~ 7

Author(s):

Qing Yu ◽

Bradley R. Postle

Keyword(s):

Working Memory ◽

Visual Cortex ◽

Brain Regions ◽

Focus Of Attention ◽

Neural Representation ◽

Stimulus Information ◽

Brain Areas ◽

Early Visual Cortex ◽

A Site ◽

Different Levels

AbstractWe tracked the neural representation of the orientation and the location of stimuli held in working memory at different levels of priority (“attended” and “unattended” memory items -- AMI and UMI), using multivariate inverted encoding models of human fMRI. Although representation of the orientation of the AMI and of the UMI could be reconstructed in several brain regions, including in early visual and parietal regions, the identity of the UMI was actively represented in early visual cortex in a distinct “reversed” code, suggesting this region as a site of the focus of attention to nonspatial stimulus information. The location of stimuli was also broadly represented, although only in parietal cortex was the location of the UMI represented in a reversed code. Our results suggest that a common recoding operation may be engaged, across stimulus dimensions and brain areas, to retain information in working memory while outside the focus of attention.

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