Quantifying and comparing the pattern of thalamic and cortical projections to the posterior auditory field in hearing and deaf cats.

Authors

Blake E Butler, Cerebral Systems Laboratory, University of Western Ontario, London, Ontario, Canada, N6A 5C2 & Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada, N6A 5C1 & Brain and Mind Institute, University of Western Ontario, London, Ontario, Canada, N6A 5B7
Nicole Chabot, Cerebral Systems Laboratory, University of Western Ontario, London, Ontario, Canada, N6A 5C2 & Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada, N6A 5C1 & Brain and Mind Institute, University of Western Ontario, London, Ontario, Canada, N6A 5B7
Stephen G Lomber, Cerebral Systems Laboratory, University of Western Ontario, London, Ontario, Canada, N6A 5C2 & Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada, N6A 5C1 & Department of Psychology, University of Western Ontario, London, Ontario, Canada, N6A 5C2 & Brain and Mind Institute, University of Western Ontario, London, Ontario, Canada, N6A 5B7 & National Centre for Audiology, University of Western Ontario, London, Ontario, Canada, N6G 1H1

Document Type

Article

Publication Date

10-15-2016

Journal

The Journal of comparative neurology

Volume

524

Issue

15

First Page

3042

Last Page

3063

URL with Digital Object Identifier

10.1002/cne.24005

Abstract

Following sensory loss, compensatory crossmodal reorganization occurs such that the remaining modalities are functionally enhanced. For example, behavioral evidence suggests that peripheral visual localization is better in deaf than in normal hearing animals, and that this enhancement is mediated by recruitment of the posterior auditory field (PAF), an area that is typically involved in localization of sounds in normal hearing animals. To characterize the anatomical changes that underlie this phenomenon, we identified the thalamic and cortical projections to the PAF in hearing cats and those with early- and late-onset deafness. The retrograde tracer biotinylated dextran amine was deposited in the PAF unilaterally, to label cortical and thalamic afferents. Following early deafness, there was a significant decrease in callosal projections from the contralateral PAF. Late-deaf animals showed small-scale changes in projections from one visual cortical area, the posterior ectosylvian field (EPp), and the multisensory zone (MZ). With the exception of these minor differences, connectivity to the PAF was largely similar between groups, with the principle projections arising from the primary auditory cortex (A1) and the ventral division of the medial geniculate body (MGBv). This absence of large-scale connectional change suggests that the functional reorganization that follows sensory loss results from changes in synaptic strength and/or unmasking of subthreshold intermodal connections. J. Comp. Neurol. 524:3042-3063, 2016. © 2016 Wiley Periodicals, Inc.