RESPONSES FROM AN ASSOCIATION AREA SECONDARILY ACTIVATED FROM OPTIC CORTEX

Abstract

Responses of an association area lying between visual and acoustic projection areas of the cat cortex were recorded, following single electric shocks applied to the optic nerve and also directly to optic cortex. Its latency in each case indicates that it is secondarily activated via the optic cortex and receives no optic radiation fibers. Stimulation at any one point of optic cortex results in response of a limited region of the secondary area, indicating point to point relations. The responses consist of weakly developed spikes superposed on a slower positive wave, followed by a weak negative wave. The response is not over 1/8 the amplitude of that of optic cortex to nerve stimulation, but otherwise similar to it. The cells in the optic cortex whose axons activate this region lie in layer IV and above, and are those which respond early in the sequence which follows nerve stimulation. Application of strychnine solution too dilute to fire spontaneous spikes permits responses of cortex adjacent to this area to follow each stimulus of the optic cortex, where no responses can be recorded without strychnine.