Abstract
Responses to electrical stimulation of the cat's retina wore recorded from single optic tract fibers. Two kinds of responses, short-latency and long-latency responses were distinguished. The short latency was about 10 msec and the long latency about 30 msec. The type of unit “on” or “off” was determined by local illumination of the center of the receptive field. In the on-unit a short-latency response was obtained at the make of a corneopositive current, but a long-latency one at the break of the current. In the off-unit a current of the opposite direction gave the same result as above. The electrical threshold of the on-unit was generally decreased by steady illumination (facilitation), but that of the off-unit was increased (inhibition) in the initial stage of illumination, but decreased (facilitation) in the later stage. The site of electrical excitation was discussed and it was suggested that the probable seat of electrical stimulation was the synaptic part between the receptor and bipolar cell at least for the on-unit. A more complicated structure was suggested for the off-unit.
