Dissociation of limbic and neocortical EEG patterns in cats under ketamine anesthesia.

✓ Studies in cats under ketamine anesthesia indicate a dissociation between the electrical activity of the thalamoneocortical areas and that of the ventral hippocampal structures. The medial area of the septum verum and the dorsal hippocampus react similarly to the thalamoneocortical circuit; however, the electrical activity of the septum verum has no direct relationship to that of the ventral hippocampal structures. Another group of cats under barbiturates did not show this dissociation in the EEG. It is suggested that the trance-like state of patients undergoing ketamine anesthesia and the hallucinatory experience in the early recovery phase may be related to the dissociated effects of the drug on the limbic and neocortical systems of the brain.

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