Visual Plasticity in the Auditory Pathway: Visual Inputs Induced into Auditory Thalamus and Cortex Illustrate Principles of Adaptive Organization in Sensory Systems

Abstract

We have induced, by appropriate surgery in newborn ferrets, retinal projections into the medial geniculate nucleus, the principal auditory thalamic nucleus. In operated animals studied as adults, retinal ganglion cells that give rise to the projection have small and medium sized somata and heterogeneous dendrite morphologies. Each retina projects to the auditory thalamus in patchy fashion. Various nuclei in auditory thalamus project normally to auditory cortex. Visual cells in auditory thalamus have circular receptive fields and receive input from slowly conducting afferents characteristic of retinal W cells. Many visual cells in primary auditory cortex have oriented receptive fields that resemble those of complex cells in striate cortex. Primary auditory cortex also contains a two dimensional visual field map. Our results carry several implications for sensory cortical function. A parsimonious explanation for the visual receptive field properties in auditory cortex is that sensory cortex carries out certain stereotypical transformations on input regardless of modality. The response features of visual cells and the two dimensional visual field map in primary auditory cortex appear to be products of adaptive organization arising from a highly divergent thalamocortical projection characteristic of the auditory system.KeywordsReceptive FieldSuperior ColliculusAuditory CortexVisual SpacePrimary Auditory CortexThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.