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

In cats under ketamine anesthesia, the electrical activity of the thalamoneocortical areas and the ventral hippocampus becomes dissociated, while the medial septum and dorsal hippocampus behave like the thalamocortical circuit. The septum's activity shows no direct link to the ventral hippocampus. This dissociation was not seen in cats given barbiturates. The authors suggest that the trance-like state during ketamine anesthesia and hallucinations during recovery may stem from this drug-induced split between limbic and neocortical brain systems.

Study at a glance

Abstract

✓ 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.