Recognition memory and theta-gamma interactions in the hippocampus.
Neuronal oscillations and cross-frequency interactions in the rat hippocampus relate in important ways to memory processes and serve as a model for studying oscillatory activity in cognition more broadly. We report here that hippocampal synchrony (CA3-CA1 coherence) increased markedly in the low gamma range as rats were exploring novel objects, particularly those for which the rat subsequently showed good memory. The gamma synchrony varied across phases of the theta rhythm such that coherence was highest at the falling slope and trough of the theta wave. Further, the shape of the theta wave was more asymmetric and elongated at the falling slope during exploration of objects for which the rat subsequently showed good memory as compared with objects for which the rat subsequently showed poor memory. The results showed a strong association between event-related gamma synchrony in rat hippocampus and memory encoding for novel objects. In addition, a novel potential mechanism of cross-frequency interactions was observed whereby dynamic alterations in the shape of theta wave related to memory in correspondence with the strength of gamma synchrony. These findings add to our understanding of how theta and gamma oscillations interact in the hippocampus in the service of memory.
['Trimper|John B|JB|', 'Stefanescu|Roxana A|RA|', 'Manns|Joseph R|JR|']
D000818:Animals D058256:Brain Waves D056547:CA1 Region, Hippocampal D056654:CA3 Region, Hippocampal D004567:Electrodes, Implanted D058407:Electroencephalography Phase Synchronization D005106:Exploratory Behavior D008297:Male D061212:Memory, Episodic D051381:Rats D020318:Rats, Long-Evans D021641:Recognition, Psychology D013826:Theta Rhythm
recognition memory hippocampus oscillations coherence gamma theta