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Published on: June 29, 2018
Gamma Oscillations and Their Cross-frequency Coupling in the Primate Hippocampus during Sleep
Saori Takeuchi1,2, Tatsuya Mima3, Rie Murai1
1Supportive Center for Brain Research, National Institute for Physiological Sciences, Okazaki, Japan.
Study Objectives:
The mechanism by which sleep consolidates memory is unclear. Based on the two-stage model of memory consolidation, different functions for slow wave sleep (SWS) and rapid eye movement (REM) sleep have been proposed; thus, state-dependent changes of neural oscillations in the hippocampus might clarify this fundamental question.
Methods:
We recorded hippocampal local field potentials from freely behaving monkeys via telemetry and analyzed their nonstationary oscillations using Hilbert-Huang transform.
Results:
By applying a recently developed empirical mode decomposition analysis, we found strong cross-frequency coupling between high-frequency and slow wave oscillations during SWS and a prominent increase of gamma band activity in short bursts during REM sleep in unanesthetized primates' hippocampus.
Conclusion:
Spatiotemporal integration through coupled oscillations during slow wave sleep might be a physiological basis of system consolidation, whereas gamma bursts during rapid eye movement sleep might be related to synaptic consolidation in the local hippocampal neural circuit.
