Electronic Thesis and Dissertation Repository


Master of Science




Lomber, Stephen G.


Following early-onset deafness, studies have demonstrated crossmodal plasticity, throughout “deaf” auditory cortex. Crossmodally reorganized auditory cortex shows increased dendritic spine density, which suggests increased numbers of axon terminals. I examined projections from the medial geniculate body (MGB) of hearing and early-deaf cats in order to reveal the distribution of synaptic boutons in the cortex, originating from MGB neurons. Anterograde fluorescent dextran tracers were deposited bilaterally in the MGB in order to label cortical axon terminals. Deafness resulted in axon terminal increases in visual cortex, and conservation of auditory axon terminal distribution. Visual areas PLLS and area 18 received increased projections from deaf MGB. Distributions of thalamocortical axon terminals in crossmodally reorganized deaf auditory areas PAF, DZ and fAES were stable. These findings indicate a need for studies of corticocortical connectivity, to find an anatomical basis for crossmodal reorganization.

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