Layer 5 and 6 neurons projecting to the inferior colliculus comprise two distinct and heterogeneous populations in the cortex

Yudintsev, Georgiy; Llano, Daniel A.

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https://hdl.handle.net/2142/95194 Copy

Description

Title

Layer 5 and 6 neurons projecting to the inferior colliculus comprise two distinct and heterogeneous populations in the cortex

Author(s)

• Yudintsev, Georgiy
• Llano, Daniel A.

Issue Date

2017-02-13

Keyword(s)

• Auditory cortex
• Cortex
• Inferior colliculus
• Top-down projections
• Descending auditory system
• In vivo imaging

Abstract

Top-down modulation is a powerful mechanism by which the brain can disambiguate signals arriving at the sensory periphery, and descending projections are believed to be an important anatomical substrate by which this modulation may occur. One of such projections - the corticocollicular projection - has recently garnered much attention due to its potential to alter response properties of cells in the inferior colliculus (IC). However, the anatomical organization of this pathway remains poorly understood. The corticocollicular neurons emanate from two distinct bands of the auditory cortex - layer 5 and deep layer 6 - and differ in their morphology and biophysical properties. The current mouse study from our laboratory demonstrates significant heterogeneity in the global distributions of layer 5 and 6 corticocollicular neurons, with layer 6 generally covering a broader area of the cortex than layer 5. As confirmed by more detailed analysis of serial reconstructions obtained in Neurolucida, we found that layer 6 cellular distribution is centered more ventrally and anteriorly than layer 5, also forming a rostro-ventral area in the cortex consisting only of layer 6 cells. Combining in vivo imaging in GCaMP mice, followed by a retrograde tracer injection and post-hoc anatomical reconstructions, we found the rostro-ventral area of layer 6 cells to be acoustically irresponsive to pure tones, noise or species specific mouse calls. Further small injections of an anterograde tracer (BDA) or retrograde tracer (CTb) into this area revealed its connections with the amygdala and a number of subcortical structures, including paralaminar thalamic nuclei. These data extend previous findings that suggest that layer 5 and layer 6 corticocollicular projections have different organizations and, presumably, different roles in modifying inferior colliculus function.

Type of Resource

• text
• image

Language

en

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http://hdl.handle.net/2142/95194

Sponsor(s)/Grant Number(s)

NIDCD R01 DC013073 02

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