SPATIOTEMPORAL RECEPTIVE-FIELDS IN CARP RETINAL HORIZONTAL CELLS

1. The dynamics of the receptive fields of retinal horizontal cells we re examined by applying a spatio-temporal modulated light signal to th e retina. 2. The spatio-temporal receptive fields of both cone-and rod -driven horizontal cells, estimated through cross-correlation between the modulated light signal and the cells' responses, showed their rece ptive fields (the space-dependent component) to be reduced in size wit h time. 3. In cone-driven horizontal cells, the reduction in receptive field size was initially small but then rapidly became prominent with time. The time to peak of the time-dependent component of spatio-temp oral receptive fields did not depend on the distance from the centre 4 . Application of a small amount of Co2+, an agent blocking the cone-dr iven horizontal cells' feedback action on cones, or GABA, resulted in a reversal of the time-dependent shrinkage of receptive fields to time -dependent expansion. 5. In rod-driven horizontal cells, the receptive field shrinkage was slow The time to peak of the time-dependent compo nent decreased with the distance from the centre. 6. Image processing experiments examining the response pattern in the horizontal cell laye r (neural image) to a moving square of light showed smudging of the ne ural image when the time-dependent receptive field expansion was prese nt, while there was essentially no smudging under conditions of recept ive field shrinkage.