Unusually large receptive fields in cats with restricted visual experience

Abstract

The receptive fields of striate cortex neurons were analyzed in cats which had restricted or no visual experience. Two groups of animals were investigated: 1. cats which were deprived from contour vision over variable periods of time up to 1 year and 2. kittens whose visual experience was restricted to vertically oriented gratings of constant spatial frequency which moved unidirectionally at a fixed distance in front of the restrained animals. In both preparations exceedingly large receptive fields (up to 20° in diameter) were encountered, especially in cells located in supragranular layers. These large receptive fields never extended over more than 2° into the ipsilateral hemifield. Their sensitivity profile was frequently asymmetric and contained discontinuities. Many of these large receptive fields consisted of several excitatory subregions which were separated from each other by as much as 15°. Often but not always the most sensitive area was located where the retinotopic map predicted the receptive field center. The orientation and direction selectivity and also the angular separation of such multiple excitatory bands often matched precisely the orientation, direction and spatial frequency of the experienced moving grating. In other fields with multiple excitatory subregions such a correspondence could not be established; the various subregions could even have different orientation and direction selectivities. From these unconventional receptive fields it is concluded that the function of cat striate cortex is not confined to a point by point analysis of the visual field in retinotopically organized and functionally isolated columns.