FFT analysis of EEG during stage 2-to-REM transitions in narcoleptic patients and normal sleepers

Abstract

The EEG in REM sleep is markedly different from the EEG in non-REM sleep; however, very little research has been conducted analyzing the transition from NREM to REM sleep. The purpose of this study was to describe the changes in EEG power spectra that coincide with significant physiological events throughout the transition from stage 2 to REM sleep. Furthermore, a comparison of the stage 2 to REM transition between narcoleptic patients and normal sleepers was conducted. Five female and five male patients diagnosed with narcolepsy-cataplexy and 10 normal sleepers matched for age and gender participated. Analyses were based on the consecutive appearance of 3 common physiological indicators of REM sleep: First, a decrease in tonic submental EMG activity; second, the appearance of saw tooth waves; and third, the appearance of rapid eye movements. Systematic changes in EEG power density were evident for delta, theta, alpha and sigma frequencies, across the stage 2-REM transition. These changes appeared to be relatively continuous throughout this transition rather than changing dramatically following the onset of any one of the 3 primary physiological indicators of REM sleep. Furthermore, the transition from stage 2 to stage REM appeared to be similar for narcoleptic patients and normal sleepers.