Transient 23-30 Hz oscillations in mouse hippocampus during exploration of novel environments.
The hippocampus is a key brain structure for the encoding of new experiences and environments. Hippocampal activity shows distinct oscillatory patterns, but the relationships between oscillations and memory are not well understood. Here we describe bursts of hippocampal approximately 23-30 Hz (beta2) oscillations in mice exploring novel, but not familiar, environments. In marked contrast to the relatively invariant approximately 8 Hz theta rhythm, beta2 power was weak during the very first lap of the novel environment, increased sharply as the mice reencountered their start point, then persisted for only a few minutes. Novelty-evoked oscillations reflected precise synchronization of individual neurons, and participating pyramidal cells showed a selective enhancement of spatial specificity. Through focal viral manipulations, we found that novelty-evoked oscillations required functional NMDA receptors in CA3, a subregion critical for fast oscillations in vitro. These findings suggest that beta2 oscillations indicate a hippocampal dynamic state that facilitates the formation of unique contextual representations.
Berke
Joshua D
JD
Department of Psychology, University of Michigan, Ann Arbor, Michigan 48104, USA. jdberke@umich.edu
Hetrick
Vaughn
V
Breck
Jason
J
Greene
Robert W
RW
D051698:Activating Transcription Factor 2 / Q000235:genetics; D000818:Animals; D004569:Electroencephalography; D005106:Exploratory Behavior / Q000502:physiology*; D006624:Hippocampus / Q000502:physiology*; D017403:In Situ Hybridization; D008297:Male; D051379:Mice; D009473:Neuronal Plasticity / Q000502:physiology*; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism; D019076:Transgenes
D051698:Activating Transcription Factor 2; C497106:Atf2 protein, mouse; D016194:Receptors, N-Methyl-D-Aspartate