POTENTIALS EVOKED IN CAT CEREBRAL CORTEX BY DIFFUSE AND BY PUNCTIFORM PHOTIC STIMULI

Abstract

Under pentobarbital anesthesia the highest amplitude of electrical response to any optic stimulation arises in a cortical region adjacent to but mostly outside of area striata. Stimuli subtending only 1[degree] and near threshold for detection of electrocortical reaction still evoke potentials in most all the "visual" cortex (including extrastriatal areas) bilaterally regardless of stimulus location. Certain regions of the retina such as area centralis produce the largest potentials throughout most of this cortex and the amplitude of the cortical responses is, in addition, greatly influenced by the inherent properties of the local cortical region. With this dual complexity only rough indications of topographical retino-cortical organization could be detected. Cortex yielding the largest and earliest "on" potentials for a flash at one point in the visual field frequently produced its most prominent "off" response when the stimulus was shifted to an antipodal location. Preliminary experiments show responses of monkey cortex to optic stimuli differ greatly from the cat.