The organization of visual receptive fields or neurons in the cat colliculus superior

The receptive field organization of neurons in the superior colliculus of the cat was investigated. Extracellular recordings from single units were made during the stimulation of their receptive fields by flashing light-spots and diffuse light illumination. According to the differences in their organizations receptive fields were classified as "homogeneous", if the response pattern to flashing spot was the same in every point of the receptive field; and "heterogeneous", if the pattern of response of the cell changed irregularly as a function of a change in the location of the flashing spot. Receptive fields were also classified according to the latency distribution throughout the receptive field. The latency of the "on" response evoked by a flashing light-spot was measured. Two types of receptive fields were observed: homolatent, if there were no significant differences in the latencies between neighboring points in the receptive field; and heterolatent, if the latencies of responses were irregularly distributed and significant differences in latencies between neighboring points existed. It is concluded that the receptive fields in the cat's colliculus superior have granular structure.