Directional coupling of slow and fast hippocampal gamma with neocortical alpha/beta oscillations in human episodic memory

Benjamin J. Griffiths, George Parish, Frederic Roux, Sebastian Michelmann, Mircea van der Plas, Luca D. Kolibius, Ramesh Chelvarajah, David T. Rollings, Vijay Sawlani, Hajo Hamer, Stephanie Gollwitzer, Gernot Kreiselmeyer, Bernhard Staresina, Maria Wimber, Simon Hanslmayr

Research output: Contribution to journalArticlepeer-review


Episodic memories hinge upon our ability to process a wide range of multisensory information and bind this information into a coherent, memorable representation. On a neural level, these 2 processes are thought to be supported by neocortical alpha/beta desynchronization and hippocampal theta/gamma synchronization, respectively. Intuitively, these 2 processes should couple to successfully create and retrieve episodic memories, yet this hypothesis has not been tested empirically. We address this by analyzing human intracranial electroencephalogram data recorded during 2 associative memory tasks. We find that neocortical alpha/beta (8 to 20 Hz) power decreases reliably precede and predict hippocampal “fast” gamma (60 to 80 Hz) power increases during episodic memory formation; during episodic memory retrieval, however, hippocampal “slow” gamma (40 to 50 Hz) power increases reliably precede and predict later neocortical alpha/beta power decreases. We speculate that this coupling reflects the flow of information from the neocortex to the hippocampus during memory formation, and hippocampal pattern completion inducing information reinstatement in the neocortex during memory retrieval.

Original languageEnglish (US)
Pages (from-to)21834-21842
Number of pages9
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number43
StatePublished - Oct 22 2019


  • Episodic memory
  • Hippocampus
  • Human
  • Intracranial EEG
  • Neural oscillations

ASJC Scopus subject areas

  • General


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