Dynamic phase-shifts between theta generators in the rat hippocampus

Winson [13] reported on two independent phase-reversed generators in the rat hippocampus. In the present study the synchrony between the two generators was investigated during the sleep-wakefulness cycle and during a behaviour-dependent discriminative learning task. Electrical activities derived from the CA 1 region and dentate gyrus were in phase during slow wave sleep but phase-reversed during the awake state and paradoxical sleep. The degree of phase-reversal was significantly higher during running than during lever pressing. These findings demonstrate that substantial changes occur within the hippocampal circuitry during dynamic shifts of behaviour.