VISUALLY EVOKED CORTICAL POTENTIALS IN AWAKE CATS DURING SACCADIC EYE-MOVEMENTS

Visually evoked potentials (VEPs) measured under conditions of retinal image stabilization that minimized the influences of visual masking a nd smearing were averaged from electroencephalographic records measure d from striate cortex of three cats. The amplitudes of the VEPs increa sed around saccade initiation. The grating-evoked potentials obtained at different times relative to the saccade exhibited changes in wavefo rm shape that could be attributed to a saccade-evoked potential. The c hanges in the shape of the waveform were reasonably accounted for by t he summation of the grating-evoked potential (produced when the cat di d not make a saccade) and an appropriately timed saccade-evoked potent ial. The fundamental amplitudes of the residual potentials were comput ed and found to vary across the time course of the saccade. These obse rvations suggest that there are other influences besides visual maskin g that are exerted early in the visual pathway to modulate visual proc essing during saccadic eye movements. A corollary discharge process is the most likely candidate to exert these influences.