[Neural mechanism of hippocampal memory organized by theta rhythm].
The firing of hippocampal principal cells in freely running rats exhibits a progressive phase retardation as the animal passes through a cell's "place" field. It is called "phase precession" and is of interest as a possible neural mechanism of the hippocampus dependent memory. We analyze the complexity of phase-position distributions of spikes by estimating the probability density functions. Although these distributions vary among different cells and regions, this complexity is well described by a superposition of two normal distribution functions, suggesting that the firing behavior consists of two components. In one, the firing phase shifts over a range of about 180 degrees. The functional relevance is further elucidated by analyzing the experience-dependent change of spike distribution. These results suggest that the temporal relation among place cells endows the selective LTP for the memory of temporal sequence. It provides a fundamental neural mechanism of episodic memory.
Yamaguchi
Yoko
Y
RIKEN Brain Science Institute, 2-1, Hirosawa, Wako, 351-0198 Japan.
D000818:Animals; D006624:Hippocampus / Q000502:physiology*; D006801:Humans; D008568:Memory / Q000502:physiology*; D009473:Neuronal Plasticity; D051381:Rats; D013569:Synapses / Q000502:physiology; D013826:Theta Rhythm / Q000523:psychology*