CEREBRAL RESPONSE IN SOMATIC AREA II OF IPSILATERAL SOMATIC I ORIGIN

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Abstract
A compound response is evoked in somatic area II by a single shock to ipsilateral somatic I of cat under Nembutal (pentobarbital-Na) anesthesia. It consists of the following deflections: (1) a large surface-positive (S), (2) 2 smaller surface-positive (PI, P2), (3) a surface-negative (D) and (4) a long-lasting surface-positive-negative (A1, A2). An attempt was made to analyse the components of the response with the use of the following experimental methods: (1) excitability characteristics determined by paired identical stimuli at various intervals and recurrence rates; (2) the effect of local cortical application of potassium cyanide and strychnine; (3) intracortical recording with a glass pipette electrode; (4) interaction between responses to somatic I and afferent stimulation; (5) interaction between responses to stimulation of somatic I and of a cortical point near the recording electrode. It is concluded that component S is of incoming volley origin, and that components P1 and P2 represent the product of postsynaptic activity within the cortex. Also, component P2 and the postsynaptic surface-positive component of the primary response evoked by afferent stimulation are largely produced by the same cortical elements, and component D is of similar origin as the "dendritic response" evoked by topical stimulation.