Research ReportDo slow and fast gamma rhythms correspond to distinct functional states in the hippocampal network?

- I propose that slow and fast gamma are distinct states in the hippocampal network.
- I present evidence that slow and fast gamma play unique roles in memory processing.
- I suggest key experiments to improve our understanding of slow and fast gamma.

For decades, hippocampal gamma was thought to be a single type of rhythm with a continuously varying frequency. However, an increasing body of evidence supports a new hypothesis regarding hippocampal gamma. The patterns traditionally defined as hippocampal gamma may actually comprise separate gamma subtypes with distinct frequencies and unique functions. The present review discusses the evidence for and against this new viewpoint. This review will also point out key questions that remain to be answered to validate the two-gamma hypothesis.This article is part of a Special Issue entitled SI: Brain and Memory.