Abolition of the hippocampal theta activity and drug-learning dissociation.

Rats were trained to escape electric shock by running into one arm of a T-maze on 10-trial daily sessions with pentobarbital (10 mg/kg), and to the opposite arm of the maze on other sessions with saline, the drug and saline sessions being alternated. This drug-learning dissociation or state-dependent learning was achieved by rats with medial septal lesions, abolishing hippocampal theta activity, as efficiently as rats with cortical lesions and intact rats. The suggested relationship between drug-learning dissociation and the suppression of hippocampal theta waves, produced by the drug, was not evidenced.