Summation for Stationary and Moving Visual Stimuli in Receptive Fields of Cat Pretectal Neurons

Numerous investigations have shown that the cat's pretectal region is involved in various visual habits and in visually guided behaviour. Thus visually driven pretectal neurons should possess summation abilities for integration of incoming sensory information. We investigated responses of 102 neurons in the pretectal region of cats with pretrigeminal brain stem transection using single-unit extracellular recording. Cells were examined with moving and stationary visual stimuli of different sizes. Our purpose was to compare summation characteristics for stationary and moving visual stimuli in the same neuron. Only a small proportion (5%) of pretectal neurons revealed similar summation characteristics for stationary and moving stimuli. The great majority of neurons showed different patterns of summation, depending on the type of the visual stimulus. For example, positive and negative effects of an increase of the stimulus size on the intensity of cellular response were observed. The results suggest that there are several discrete mechanisms subserving integration of sensory information concerning stationary and moving visual stimuli.