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Nonlinearity of the inhibition underlying retinal directional selectivity

Published online by Cambridge University Press:  02 June 2009

Franklin R. Amthor
Affiliation:
Department of Psychology and Neurobiology Research Center, University of Alabama at Birmingham, Birmingham
Norberto M. Grzywacz
Affiliation:
Center for Biological Information Processing, Massachusetts Institute of Technology, Cambridge, and The Smith-Kettlewell Eye Research Institute, San Franciso

Abstract

An important mechanism for the discrimination of direction of motion in the retina is a spatially asymmetric inhibition. This inhibition has been postulated to operate either as a subtraction, like in difference-of-Gaussians' models, or as a division, like in shunting-inhibition models of directional selectivity. The latter, but not the former, is nonlinear. This raises the question of whether the inhibitory mechanism involved in directional selectivity is nonlinear. To investigate this issue, we studied the linearity of the contrast dependence of the extracellularly recorded responses to apparent motions in ON-OFF directionally selective ganglion cells of the rabbit retina. The results show that the inhibition underlying directional selectivity is nonlinear and fits shunting-inhibition models well. Other biophysical mechanisms that might account for the type of nonlinearity observed in the data are also considered.

Information

Type
Research Articles
Copyright
Copyright © Cambridge University Press 1991

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