Decrease in gamma-band activity tracks sequence learning

Radhika Madhavan, Daniel Millman, Hanlin Tang, Nathan E. Crone, Fredrick A. Lenz, Travis S. Tierney, Joseph R. Madsen, Gabriel Kreiman, William S. Anderson

Research output: Contribution to journalArticlepeer-review


Learning novel sequences constitutes an example of declarative memory formation, involving conscious recall of temporal events. Performance in sequence learning tasks improves with repetition and involves forming temporal associations over scales of seconds to minutes. To further understand the neural circuits underlying declarative sequence learning over trials, we tracked changes in intracranial field potentials (IFPs) recorded from 1142 electrodes implanted throughout temporal and frontal cortical areas in 14 human subjects, while they learned the temporal-order of multiple sequences of images over trials through repeated recall. We observed an increase in power in the gamma frequency band (30–100 Hz) in the recall phase, particularly in areas within the temporal lobe including the parahippocampal gyrus. The degree of this gamma power enhancement decreased over trials with improved sequence recall. Modulation of gamma power was directly correlated with the improvement in recall performance. When presenting new sequences, gamma power was reset to high values and decreased again after learning. These observations suggest that signals in the gamma frequency band may play a more prominent role during the early steps of the learning process rather than during the maintenance of memory traces.

Original languageEnglish (US)
Article number222
JournalFrontiers in Systems Neuroscience
Issue numberJAN
StatePublished - Jan 21 2015


  • Field potentials
  • Gamma frequency oscillations
  • Human neurophysiology
  • Intracranial recordings
  • Memory
  • Sequence learning

ASJC Scopus subject areas

  • Neuroscience (miscellaneous)
  • Developmental Neuroscience
  • Cognitive Neuroscience
  • Cellular and Molecular Neuroscience

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