Dataset Information

Sensory cortex limits cortical maps and drives top-down plasticity in thalamocortical circuits.

ABSTRACT: The primary somatosensory cortex (S1) contains a complete body map that mirrors the subcortical maps developed by peripheral sensory input projecting to the sensory hindbrain, the thalamus and then S1. Peripheral changes during development alter these maps through 'bottom-up' plasticity. Unknown is how S1 size influences map organization and whether an altered S1 map feeds back to affect subcortical maps. We show that the size of S1 in mice is significantly reduced by cortex-specific deletion of Pax6, resulting in a reduced body map and loss of body representations by an exclusion of later-differentiating sensory thalamocortical input. An initially normal sensory thalamus was repatterned to match the aberrant S1 map by apoptotic deletion of thalamic neurons representing body parts with axons excluded from S1. Deleted representations were rescued by altering competition between thalamocortical axons using sensory deprivation or increasing the size of S1. Thus, S1 size determined the resolution and completeness of body maps and engaged 'top-down' plasticity that repatterned the sensory thalamus to match S1.

SUBMITTER: Zembrzycki A

PROVIDER: S-EPMC3769112 | biostudies-literature | 2013 Aug

REPOSITORIES: biostudies-literature

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Sensory cortex limits cortical maps and drives top-down plasticity in thalamocortical circuits.

Zembrzycki Andreas A Chou Shen-Ju SJ Ashery-Padan Ruth R Stoykova Anastassia A O'Leary Dennis D M DD

Nature neuroscience 20130707 8

The primary somatosensory cortex (S1) contains a complete body map that mirrors the subcortical maps developed by peripheral sensory input projecting to the sensory hindbrain, the thalamus and then S1. Peripheral changes during development alter these maps through 'bottom-up' plasticity. Unknown is how S1 size influences map organization and whether an altered S1 map feeds back to affect subcortical maps. We show that the size of S1 in mice is significantly reduced by cortex-specific deletion of ...[more]

PMID: 23831966

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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

Sensory cortex limits cortical maps and drives top-down plasticity in thalamocortical circuits.

Publications

Sensory cortex limits cortical maps and drives top-down plasticity in thalamocortical circuits.

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