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Keywords:

  • alpha band component;
  • sequential analysis;
  • sleep EEG;
  • sleep onset

Abstract

The purpose of this research is to elucidate the amplitude variations of alpha band component in human electroencephalographic records during the transition between wakefulness and stage 1 sleep. The records from 16 adult male subjects were mathematically analyzed in successive 3-s epochs using a unique method of calculation (RLSSR). Amplitude variations are described herein. (i) General amplitudes are high during wakefulness and low during stage 1 sleep. Irregular fluctuations in amplitude are superimposed on these two levels. (ii) A large, steep, characteristic decline occurs during wakefulness. Two EEG patterns at the bottom of the decline represent arousal and EEG in stage 1 sleep, and these are referred to as big-decline-w and big-decline-s. The transition between the two levels appears as a big-decline-s rather than a gradual decrease. (iii) Thirteen records showed a multiple big-decline-s pattern before stage 1 sleep. The period from the first to the last big-decline-s is referred to as the “approach period” to sleep. Three subjects had no such approach and only one big-decline-s that appeared at the end of wakefulness. (iv) The bottom of the last big-decline-s of the three sites, occipital, central and frontal, appeared simultaneously in 6 subjects, 9 had a one-epoch gap, and 1 had two such gaps. The decline of the slope of the last big-decline-s showed high regression to an exponential curve. It is suggested that this characteristic pattern is the significant index of psychophysiological transition from wakefulness to sleep.