Hippocampal pattern completion is linked to gamma power increases and alpha power decreases during recollection

Research output: Contribution to journalArticle

Authors

  • Sebastian Michelmann
  • Mathilde Bonnefond
  • Nikolai Axmacher
  • Juergen Fell

External organisations

  • School of Psychology, The University of Birmingham, Birmingham, United Kingdom
  • Faculty of Psychology, Ruhr University Bochum, Bochum, Germany.
  • Department of Epileptology, University of Bonn, Bonn, Germany.
  • Radboud University Nijmegen, Donders Institute for Brain, Behaviour and Cognition, Nijmegen, Netherlands

Abstract

How do we retrieve vivid memories upon encountering a simple cue? Computational models suggest that this feat is accomplished by pattern completion processes involving the hippocampus. However, empirical evidence for hippocampal pattern completion and its underlying mechanisms has remained elusive. Here, we recorded direct intracranial EEG as human participants performed an associative memory task. For each study (encoding) and test (retrieval) event, we derived time-frequency resolved representational patterns in the hippocampus and compared the extent of pattern reinstatement for different mnemonic outcomes. Results show that successful associative recognition (AR) yields enhanced event-specific reinstatement of encoding patterns compared to non-associative item recognition (IR). Moreover, we found that gamma power (50–90 Hz) increases – in conjunction with alpha power (8–12 Hz) decreases not only distinguish AR from IR, but also correlate with the level of hippocampal reinstatement. These results link single-shot hippocampal pattern completion to episodic recollection and reveal how oscillatory dynamics in the gamma and alpha bands orchestrate these mnemonic processes.

Details

Original languageEnglish
Article numbere17397
Number of pages18
JournalElife
Volume5
Publication statusPublished - 10 Aug 2016

Keywords

  • episodic memory, hippocampus, intracranial EEG, neural oscillations, pattern completion