MULTIPLE RESPONSE AND EXCITABILITY OF CAT'S VISUAL CORTEX

Abstract

The evoked cortical response to electrical stimulation in the visual system of the cat was studied in an effort to determine the nature of the compound cortical potential. Studies were made of latency differences for the 4 surface-positive waves of the evoked response, when stimuli were applied to different distances from the cortex. The effect of local cortical application of procaine was evaluated. The alterations produced by the degree of continuous retinal illumination were examined. Excitability characteristics were determined with the use of paired identical stimuli at various intervals and recurrence rates. The response from the exposed white matter was also studied after removal of the visual cortex. The literature is reviewed and the similarities and discrepancies discussed. It is suggested from these experiments that the first two surface-positive waves represent the arrival of the impulses traversing respectively fast and slow conducting fiber groups of the white matter, and that the 3rd and 4th surface-positive waves represent the cortical response to the arrival on the 1st and 2d waves.