Suppression of gamma activity in the human medial temporal lobe by sevoflurane anesthesia

Sunao Uchida*, Hideto Nakayama, Taketoshi Maehara, Nobuhide Hirai, Hiroshi Arakaki, Motoaki Nakamura, Tetsuo Nakabayashi, Hiroyuki Shimizu

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

34 Citations (Scopus)


We have reported the presence of continuous gamma (30-150 Hz) activity in the human medial temporal lobe (MTL). Since the MTL is involved in learning and memory, we speculated that MTL gamma activity is related to such higher brain functions. It is thus of interest to learn how this activity changes during different states of consciousness. In this study, we recorded electrococorticographic (ECoG) activity directly from the surface of the MTL after various doses of sevoflurane anesthesia. Five epileptic patients underwent electrode placement operations in which electrodes were attached to the surfaces of the MTL and the basal temporal lobe (BTL). Immediately following the operation ECoG was recorded from each patient under four concentrations of sevoflurane anesthesia (1.5, 2.0, 2.5 and 3.0%). Fast Fourier Transform (FFT) analysis was performed on the MTL ECoGs. Under the lowest sevoflurane concentration, MTL gamma activity was observed in all patients. However, gamma activity was progressively suppressed by increased concentrations of sevoflurane, in a dose-dependent manner. Sevoflurane has been known to reduce neuronal excitability in the rat hippocampus in vitro, probably by changing GABAergic inhibition. The reduction of MTL gamma in the present study may be the result of such a mechanism. Although memory function was not tested in this study, the amount of MTL gamma activity may be related to residual memory function during anesthesia.

Original languageEnglish
Pages (from-to)39-42
Number of pages4
Issue number1
Publication statusPublished - 2000 Jan 17
Externally publishedYes


  • Gamma
  • Human medial temporal lobe
  • Sevoflurane anesthesia

ASJC Scopus subject areas

  • Neuroscience(all)


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