1971 Volume 14 Issue 6 Pages 604-610
This investigation was carried out to study auditory cortical responses that could be recorded from the scalp, dura and brain of the rhesus monkeys.
In the alert monkey the averaged cortical response with the early wave components (P1 and N1) being the largest and most consistent, could be recorded from the scalp near the vertex and was maximally recorded from the precentral dura.
During anesthesia the averaged cortical response could be maximally recorded from the dura over the middle portion of the superior temporal lobe. Compared with the alert state the P1 and N1 waves greatly diminished in amplitude during anesthesia, but did not change significantly in latency. On the other hand, the P2 and N2 waves greatly increased in amplitude and became longer in latency.
In the alert state, scalp response thresholds were poorer than intracranial ones. Intracranial response thresholds were lowest during sedation with phencyclidine hydrochloride and progressively became worse during the anesthetized state and highest in the alert state.