Regional specialization of visual cortex in congenital blindness reveals takeover by multiple distinct top-down fronto-parietal inputs

AbstractStudies of sensory loss are a model for understanding the functional flexibility of human cortex. In congenital blindness, subsets of visual cortex are recruited during higher-cognitive tasks, such as language and math tasks. Is such dramatic functional repurposing possible throughout the lifespan or restricted to sensitive periods in development? We compared visual cortex function in individuals who lost their vision as adults (after age 17) to congenitally blind and sighted blindfolded adults. Participants took part in resting-state and task-based fMRI scans during which they solved math equations of varying difficulty and judged the meanings of sentences. Blindness at any age caused “visual” cortices to synchronize with specific fronto-parietal networks at rest. However, in task-based data, visual cortices showed regional specialization for math and language and load-dependent activity only in congenital blindness. Thus, despite the presence of long-range functional connectivity, cognitive repurposing of human cortex is limited by sensitive periods.

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Sensitive Period for Cognitive Repurposing of Human Visual Cortex

Cerebral Cortex ◽

10.1093/cercor/bhy280 ◽

2018 ◽

Vol 29 (9) ◽

pp. 3993-4005 ◽

Cited By ~ 6

Author(s):

Shipra Kanjlia ◽

Rashi Pant ◽

Marina Bedny

Keyword(s):

Visual Cortex ◽

Sensory Loss ◽

Sensitive Period ◽

Human Cortex ◽

Regional Specialization ◽

Congenital Blindness ◽

Functional Flexibility ◽

Sensitive Periods ◽

Congenitally Blind ◽

Visual Cortices

Abstract Studies of sensory loss are a model for understanding the functional flexibility of human cortex. In congenital blindness, subsets of visual cortex are recruited during higher-cognitive tasks, such as language and math tasks. Is such dramatic functional repurposing possible throughout the lifespan or restricted to sensitive periods in development? We compared visual cortex function in individuals who lost their vision as adults (after age 17) to congenitally blind and sighted blindfolded adults. Participants took part in resting-state and task-based fMRI scans during which they solved math equations of varying difficulty and judged the meanings of sentences. Blindness at any age caused “visual” cortices to synchronize with specific frontoparietal networks at rest. However, in task-based data, visual cortices showed regional specialization for math and language and load-dependent activity only in congenital blindness. Thus, despite the presence of long-range functional connectivity, cognitive repurposing of human cortex is limited by sensitive periods.

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Top-down control of visual cortex by the frontal eye fields through oscillatory realignment

Nature Communications ◽

10.1038/s41467-021-21979-7 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Domenica Veniero ◽

Joachim Gross ◽

Stephanie Morand ◽

Felix Duecker ◽

Alexander T. Sack ◽

...

Keyword(s):

Visual Cortex ◽

Transcranial Magnetic Stimulation ◽

Visual Perception ◽

Magnetic Stimulation ◽

Single Pulse ◽

Frontal Eye Fields ◽

Phase Reset ◽

Top Down ◽

Visual Areas ◽

Beta Frequency

AbstractVoluntary allocation of visual attention is controlled by top-down signals generated within the Frontal Eye Fields (FEFs) that can change the excitability of lower-level visual areas. However, the mechanism through which this control is achieved remains elusive. Here, we emulated the generation of an attentional signal using single-pulse transcranial magnetic stimulation to activate the FEFs and tracked its consequences over the visual cortex. First, we documented changes to brain oscillations using electroencephalography and found evidence for a phase reset over occipital sites at beta frequency. We then probed for perceptual consequences of this top-down triggered phase reset and assessed its anatomical specificity. We show that FEF activation leads to cyclic modulation of visual perception and extrastriate but not primary visual cortex excitability, again at beta frequency. We conclude that top-down signals originating in FEF causally shape visual cortex activity and perception through mechanisms of oscillatory realignment.

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Neural modulation of a realistic layered-microcircuit model of visual cortex based on bottom-up and top-down signals

Neuroscience Research ◽

10.1016/j.neures.2010.07.1684 ◽

2010 ◽

Vol 68 ◽

pp. e380

Author(s):

Tomoki Fukai ◽

Nobuhiko Wagatsuma ◽

Tobias C. Potjans ◽

Markus Diesmann

Keyword(s):

Visual Cortex ◽

Top Down ◽

Bottom Up ◽

Neural Modulation

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Bottom-up saliency and top-down learning in the primary visual cortex of monkeys

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1803854115 ◽

2018 ◽

Vol 115 (41) ◽

pp. 10499-10504 ◽

Cited By ~ 14

Author(s):

Yin Yan ◽

Li Zhaoping ◽

Wu Li

Keyword(s):

Visual Cortex ◽

Primary Visual Cortex ◽

Detection Task ◽

Late Response ◽

Late Component ◽

Neuronal Responses ◽

Top Down ◽

Bottom Up ◽

Response Component ◽

Orientation Contrast

Early sensory cortex is better known for representing sensory inputs but less for the effect of its responses on behavior. Here we explore the behavioral correlates of neuronal responses in primary visual cortex (V1) in a task to detect a uniquely oriented bar—the orientation singleton—in a background of uniformly oriented bars. This singleton is salient or inconspicuous when the orientation contrast between the singleton and background bars is sufficiently large or small, respectively. Using implanted microelectrodes, we measured V1 activities while monkeys were trained to quickly saccade to the singleton. A neuron’s responses to the singleton within its receptive field had an early and a late component, both increased with the orientation contrast. The early component started from the outset of neuronal responses; it remained unchanged before and after training on the singleton detection. The late component started ∼40 ms after the early one; it emerged and evolved with practicing the detection task. Training increased the behavioral accuracy and speed of singleton detection and increased the amount of information in the late response component about a singleton’s presence or absence. Furthermore, for a given singleton, faster detection performance was associated with higher V1 responses; training increased this behavioral–neural correlate in the early V1 responses but decreased it in the late V1 responses. Therefore, V1’s early responses are directly linked with behavior and represent the bottom-up saliency signals. Learning strengthens this link, likely serving as the basis for making the detection task more reflexive and less top-down driven.

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Layer-dependent multiplicative effects of spatial attention on contrast responses in human early visual cortex

10.1101/2020.02.01.926303 ◽

2020 ◽

Cited By ~ 1

Author(s):

Fanhua Guo ◽

Chengwen Liu ◽

Chencan Qian ◽

Zihao Zhang ◽

Kaibao Sun ◽

...

Keyword(s):

Visual Cortex ◽

Spatial Attention ◽

Middle Layer ◽

Additive Effect ◽

List Type ◽

Strong Nonlinearity ◽

Top Down ◽

Contrast Gain ◽

Early Visual Cortex ◽

Deep Layers

AbstractAttention mechanisms at different cortical layers of human visual cortex remain poorly understood. Using submillimeter-resolution fMRI at 7T, we investigated the effects of top-down spatial attention on the contrast responses across different cortical depths in human early visual cortex. Gradient echo (GE) T2* weighted BOLD signal showed an additive effect of attention on contrast responses across cortical depths. Compared to the middle cortical depth, attention modulation was stronger in the superficial and deep depths of V1, and also stronger in the superficial depth of V2 and V3. Using ultra-high resolution (0.3mm in-plane) balanced steady-state free precession (bSSFP) fMRI, a multiplicative scaling effect of attention was found in the superficial and deep layers, but not in the middle layer of V1. Attention modulation of low contrast response was strongest in the middle cortical depths, indicating baseline enhancement or contrast gain of attention modulation on feedforward input. Finally, the additive effect of attention on T2* BOLD can be explained by strong nonlinearity of BOLD signals from large blood vessels, suggesting multiplicative effect of attention on neural activity. These findings support that top-down spatial attention mainly operates through feedback connections from higher order cortical areas, and a distinct mechanism of attention may also be associated with feedforward input through subcortical pathway.HighlightsResponse or activity gain of spatial attention in superficial and deep layersContrast gain or baseline shift of attention in V1 middle layerNonlinearity of large blood vessel causes additive effect of attention on T2* BOLD

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