Neuron
Volume 82, Issue 3, 7 May 2014, Pages 670-681
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Article
Slow and Fast Gamma Rhythms Coordinate Different Spatial Coding Modes in Hippocampal Place Cells

https://doi.org/10.1016/j.neuron.2014.03.013Get rights and content
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Highlights

  • Place cells code current location during fast gamma

  • Place cells predict upcoming locations during slow gamma

  • Spikes precess across the full range of theta phases during fast gamma

  • Place cells mainly spike in the first half of their fields during slow gamma

Summary

Previous work has hinted that prospective and retrospective coding modes exist in hippocampus. Prospective coding is believed to reflect memory retrieval processes, whereas retrospective coding is thought to be important for memory encoding. Here, we show in rats that separate prospective and retrospective modes exist in hippocampal subfield CA1 and that slow and fast gamma rhythms differentially coordinate place cells during the two modes. Slow gamma power and phase locking of spikes increased during prospective coding; fast gamma power and phase locking increased during retrospective coding. Additionally, slow gamma spikes occurred earlier in place fields than fast gamma spikes, and cell ensembles retrieved upcoming positions during slow gamma and encoded past positions during fast gamma. These results imply that alternating slow and fast gamma states allow the hippocampus to switch between prospective and retrospective modes, possibly to prevent interference between memory retrieval and encoding.

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