Cortical oscillations in human medial temporal lobe during wakefulness and all-night sleep

Sunao Uchida, Taketoshi Maehara, Nobuhide Hirai, Yoshiro Okubo, Hiroyuki Shimizu

Research output: Contribution to journalArticle

43 Citations (Scopus)

Abstract

We have recorded human medial temporal lobe electrocorticogram during wakefulness and natural sleep in epileptic patients with subdural electrodes. From these recordings, we have found gamma (30-150 Hz) [Neuroscience 90 (1999) 1149] and beta-1 (10-20 Hz) [NeuroReport 10 (1999) 3055] activities during wakefulness in human medial temporal lobe. In this paper, we will report changes of these frequencies across wake and natural sleep. Electrocorticograms during wake, slow wave sleep and rapid eye movement (REM) sleep were subjected to fast Fourier transformation analysis. During wake two spectral enhancements, beta-1 and gamma, were consistently observed across subjects. In the raw signal, beta-1 was observed as a regular rhythmic oscillation. In slow wave sleep, the beta-1 peak disappeared but gamma remained, although slightly reduced in power. During REM sleep, beta-1 appeared again, but the peak frequency was significantly lower than during wake (mean frequency: wake=16.6, REM=12.8 Hz). The gamma peak was also present in REM sleep. It has been known that the rhythmic slow activity (RSA) or theta is observed in some animals. However, it is unclear whether the human hippocampus displays similar activity. Since human beta-1 appears during wake and REM sleep when RSA is observed in other species, and since beta-1 is also a regular rhythmic oscillation, we propose that beta-1 may be the functional equivalent of hippocampal RSA (theta) observed in some animals. Functional significances of the gamma activity should be further investigated.

Original languageEnglish
Pages (from-to)7-19
Number of pages13
JournalBrain Research
Volume891
Issue number1-2
DOIs
Publication statusPublished - 2001 Feb 9
Externally publishedYes

Keywords

  • Beta-1
  • Electrocorticogram
  • Gamma
  • Medial temporal lobe
  • Rhythmic slow activity

ASJC Scopus subject areas

  • Neuroscience(all)

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