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The Journal of Neuroscience, September 15, 1999, 19(18):7940-7950

Cross-Modal Reorganization of Horizontal Connectivity in Auditory Cortex without Altering Thalamocortical Projections

W.-J. Gao and S. L. Pallas

Department of Biology, Georgia State University, Atlanta, Georgia 30302

The development of the different, highly specialized regions of the mammalian cerebral cortex depends in part on neural activity, either intrinsic spontaneous activity or externally driven sensory activity. To determine whether patterned sensory activity instructs the development of intrinsic cortical circuitry, we have experimentally altered the modality of sensory inputs to cerebral cortex. Neonatal diversion of retinal axons to the auditory thalamus (cross-modal rewiring) results in a primary auditory cortex (AI) that resembles visual cortex in its response properties and topography (Roe et al., 1990, 1992). To test the hypothesis that the visual response properties are created by a visually driven reorganization of auditory cortical circuitry, we investigated the effect of early visual experience on the development of intrinsic, horizontal connections within AI. Horizontal connections are likely to play an important role in the construction of visual response properties in AI as they do in visual cortex. Here we show that early visual inputs to auditory thalamus can reorganize horizontal connections in AI, causing both an increase in their extent and a change in pattern, so that projections are not restricted to the isofrequency axis, but extend in a more isotropic pattern around the injection site. Thus, changing afferent modality, without altering the source of the thalamocortical axons, can profoundly alter cortical circuitry. Similar changes may underlie cortical compensatory processes in deaf or blind humans and may also have played a role in the parcellation of neocortex during mammalian evolution.

Key words: cortical development; sensory cortex; cross-modal plasticity; retinal axons; activity; biotinylated dextran amine; visual development; cortical circuitry; ferret

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Copyright © 1999 Society for Neuroscience  0270-6474/99/19187940-11$05.00/0

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				J. Syka Plastic Changes in the Central Auditory System After Hearing Loss, Restoration of Function, and During Learning Physiol Rev, July 1, 2002; 82(3): 601 - 636. [Abstract] [Full Text] [PDF]

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