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

Research output: Contribution to journalArticlepeer-review


  • Benjamin Griffiths
  • Sebastian Michelmann
  • Mircea Van Der Plas
  • Luca Kolibius
  • Ramesh Chelvarajah
  • David Rollings
  • Vijay Sawlani
  • Hajo Hamer
  • Stephanie Gollwitzer
  • Gernot Kreiselmeyer


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 two processes are thought to be supported by neocortical alpha/beta desynchronisation and hippocampal theta/gamma synchronisation, respectively. Intuitively, these two processes should couple to successfully create and retrieve episodic memories, yet this hypothesis has not been tested empirically. We address this by analysing human intracranial EEG data recorded during two associative memory tasks. We find that neocortical alpha/beta (8-20Hz) power decreases reliably precede and predict hippocampal “fast” gamma (60-80Hz) power increases during episodic memory formation; during episodic memory retrieval however, hippocampal “slow” gamma (40-50Hz) power increases reliably precede and predict later neocortical alpha/beta power decreases. We speculate that this coupling reflects the flow of information from neocortex to hippocampus during memory formation, and hippocampal pattern completion inducing information reinstatement in the neocortex during memory retrieval.


Original languageEnglish
Pages (from-to)21834-21842
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number43
Early online date9 Oct 2019
Publication statusPublished - 22 Oct 2019


  • episodic memory, neural oscillations, intracranial EEG, hippocampus, human