Electrical Activity of Rolandic Region in Unanesthetized Monkey

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Abstract
The electrical activity of the Rolandic region was studied in 6 unanesthetized monkeys with implanted electrodes. A rhythmic activity of 25 to 30/second and semi-rhythmic activity of up to 45/second were recorded maximally in front of the central fissure. Postcentral electrical activity was predominantly slower and consisted primarily of irregular complex 3 to 8/second activity and occasional small bursts of 8/second alpha activity. The postcentral pattern predominated in scalp recordings. During movement of the appropriate portion of the contralateral extremity there was a blocking of the usual rhythmic Rolandic activity accompanied by the appearance of low voltage 50 to 80 per second activity of about 1 second duration. This fast activity appeared maximally just anterior to the central fissure, but can be recorded in all Rolandic leads. Tactile stimulation elicited an evoked response only in the contralateral postcentral gyrus. Under anesthesia the latency of the evoked response was prolonged. It is concluded that the central fissure can be regarded as an approximate boundary in a continuous gradient of spontaneous and evoked electrical activity.