Spatial and chromatic interactions in the lateral geniculate body of the rhesus monkey.

Abstract

In the 4 dorsal (small cell) layers of the rhesus monkey lateral geniculate body 3 types of cells were distinguished. Type I cells were by far the most common. In the light-adapted state they had concentrically arranged receptive fields which were divided into an excitatory or inhibitory center and an opponent surround, the center and surround having different spectral sensitivities. Chromatic adaptation studies suggested that these cells had connections with 1 of the 3 types of cones in the field center, and another in the surround. Type II cells lacked any center-surround receptive-field arrangement, but gave opponent-color responses over all regions of the receptive field. They behaved as though they received opponent inputs from 2 sets of cones with identical distributions over the retina. Type IT1 cells had concentrically arranged on-center or off-center receptive fields, the center and surround having identical spectral sensitivities. In dark adaptation some cells behaved as though they had no connections with rods, while others showed clear evidence for both rod and cone input. All of the cell types were seen in both pairs of dorsal layers, and there were only minor differences in distributions of cell types in these 4 layers, Ventral layer cells were of 2 kinds. The 1st seemed similar to Type HI. The 2nd, termed Type IV, had concentrically arranged on-center fields with a very large off-surround whose spectral sensitivity was displaced to the red with respect to that of the center.