Independent dynamics of low, intermediate, and high frequency spectral intracranial EEG activities during human memory formation

Victoria S. Marks, Krishnakant V. Saboo, Çağdaş Topçu, Michal Lech, Theodore P. Thayib, Petr Nejedly, Vaclav Kremen, Gregory A. Worrell, Michal T. Kucewicz

Research output: Contribution to journalArticlepeer-review


A wide spectrum of brain rhythms are engaged throughout the human cortex in cognitive functions. How the rhythms of various frequency ranges are coordinated across the space of the human cortex and time of memory processing is inconclusive. They can either be coordinated together across the frequency spectrum at the same cortical site and time or induced independently in particular bands. We used a large dataset of human intracranial electroencephalography (iEEG) to parse the spatiotemporal dynamics of spectral activities induced during formation of verbal memories. Encoding of words for subsequent free recall activated low frequency theta, intermediate frequency alpha and beta, and high frequency gamma power in a mosaic pattern of discrete cortical sites. A majority of the cortical sites recorded activity in only one of these frequencies, except for the visual cortex where spectral power was induced across multiple bands. Each frequency band showed characteristic dynamics of the induced power specific to cortical area and hemisphere. The power of the low, intermediate, and high frequency activities propagated in independent sequences across the visual, temporal and prefrontal cortical areas throughout subsequent phases of memory encoding. Our results provide a holistic, simplified model of the spectral activities engaged in the formation of human memory, suggesting an anatomically and temporally distributed mosaic of coordinated brain rhythms.

Original languageEnglish (US)
Article number118637
StatePublished - Dec 15 2021


  • Alpha
  • Beta
  • Brain rhythms
  • Cognitive functions
  • Declarative memory
  • ECoG
  • Gamma
  • Intracranial EEG
  • Neuroscience
  • Spectral analysis
  • Stereo EEG
  • Theta

ASJC Scopus subject areas

  • Neurology
  • Cognitive Neuroscience


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