Synchronization of neural oscillations as a possible mechanism underlying episodic memory: a study of theta rhythm in the hippocampus.

Rat hippocampal cells exhibit characteristic phase-dependent firings when oscillation in frequency range around 8Hz is present. Based on the hypothesis that theta phase coding is generated by synchronization of neural activities, an autoassociative network model of the hippocampus and the entorhinal cortex was analyzed to explore mechanisms underlying episodic memory. Phase coding in theta rhythm enables instantaneous acquisition of experienced events including temporal and spatial contents. Further comparison with electrophysiological data from both rodents and primates suggests a possible role of theta oscillations in memory encoding and online processing of episodic events.