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Specificity of neuronal responses in primary visual cortex is modulated by interhemispheric corticocortical input.

ABSTRACT: Within the visual cortex, it has been proposed that interhemispheric interactions serve to re-establish the continuity of the visual field across its vertical meridian (VM) by mechanisms similar to those used by intrinsic connections within a hemisphere. However, other specific functions of transcallosal projections have also been proposed, including contributing to disparity tuning and depth perception. Here, we consider whether interhemispheric connections modulate specific response properties, orientation and direction selectivity, of neurons in areas 17 and 18 of the ferret by combining reversible thermal deactivation in one hemisphere with optical imaging of intrinsic signals and single-cell electrophysiology in the other hemisphere. We found interhemispheric influences on both the strength and specificity of the responses to stimulus orientation and direction of motion, predominantly at the VM. However, neurons and domains preferring cardinal contours, in particular vertical contours, seem to receive stronger interhemispheric input than others. This finding is compatible with interhemispheric connections being involved in horizontal disparity tuning. In conclusion, our results support the view that interhemispheric interactions mainly perform integrative functions similar to those of connections intrinsic to one hemisphere.

SUBMITTER: Schmidt KE

PROVIDER: S-EPMC2978237 | biostudies-literature | 2010 Dec

REPOSITORIES: biostudies-literature

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Specificity of neuronal responses in primary visual cortex is modulated by interhemispheric corticocortical input.

Schmidt Kerstin E KE Lomber Stephen G SG Innocenti Giorgio M GM

Cerebral cortex (New York, N.Y. : 1991) 20100308 12

Within the visual cortex, it has been proposed that interhemispheric interactions serve to re-establish the continuity of the visual field across its vertical meridian (VM) by mechanisms similar to those used by intrinsic connections within a hemisphere. However, other specific functions of transcallosal projections have also been proposed, including contributing to disparity tuning and depth perception. Here, we consider whether interhemispheric connections modulate specific response properties ...[more]

PMID: 20211943

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Project description:Unified visual perception relies on the integration of bottom-up and top-down inputs in the primary visual cortex (V1), with top-down inputs known to provide behavior-related modulation on visual processing. However, the organization of top-down inputs in V1 remains unclear. Here, using optogenetics-assisted circuit mapping, we characterized how multiple top-down inputs from higher-order cortical and thalamic areas engage excitatory and inhibitory neurons in V1. Systematic layer- and cell-type-specific profiling of the innervation properties of top-down inputs ultimately revealed that each top-down input employs a unique laminar profile when innervating V1. These profiles partially overlap in superficial layers, bypass layer 4 (L4), and clearly segregate upon reaching deep layers. Specifically, inputs from the medial secondary visual cortex (V2M) and anterior cingulate cortex (ACA) preferentially activate L6 neurons, while inputs from the ventrolateral orbitofrontal cortex (ORBvl) and lateral posterior thalamic nucleus (LP) activate L5 neurons. Having defined the inputs, we conducted independent optogenetic activation studies and discovered that ORBvl and LP inputs selectively activate two types of pyramidal neurons (Pyrs) in L5: Pyr <-- ORBvl and Pyr <-- LP neurons, each with specific electrophysiological properties and gene expression profiles. Retrograde mapping subsequently revealed that Pyr <-- ORBvl neurons preferentially innervate subcortical areas and Pyr <-- LP neurons innervate cortical areas, indicating parallel processing of ORBvl and LP inputs in Pyr-type-specific subnetworks. Further, we found mutual inhibition between these two subnetworks, as LP inputs indirectly inhibit Pyr <-- ORBvl neurons and ORBvl inputs inhibit Pyr <-- LP neurons through local inhibitory neurons. Our study thus deepens understanding of the neuronal mechanisms involved in top-down modulation of visual processing by providing a valuable resource characterizing the layer- and cell-type-specific organization of top-down inputs in V1 and by revealing that L5 Pyr-type-specific subnetworks engage in parallel processing of corticocortical and thalamocortical top-down inputs.

Dataset Information

Specificity of neuronal responses in primary visual cortex is modulated by interhemispheric corticocortical input.

Publications

Specificity of neuronal responses in primary visual cortex is modulated by interhemispheric corticocortical input.

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