Summation effects in receptive fields of the cat's pretectal neurons to stationary and moving visual stimuli.

1. Numerous investigations have shown that the cat's pretectal region (PR) is involved in performance of various visual habits, visually guided behaviour and learning processes. Thus, visually driven PR neurons must have abilities to integrate incoming sensory information. 2. Responses of 102 PR neurons to moving and stationary visual stimuli were investigated in cats. Special attention was paid to the comparative characteristics of summation processes in the same neuron elicited by stationary and moving visual stimuli. 3. The results indicate that only a small proportion (20%) of pretectal neurons revealed similar courses of summation for stationary and moving stimuli. The great majority of neurons (about 80%) showed differentiated courses of summation, depending on the type of visual stimuli used. 4. These data indicate that there are probably discrete mechanisms in the PR which contribute to integration of sensory information in the visually sensitive cells according to the different types of visual stimuli used.