Association between phase coupling of respiratory sinus arrhythmia and brain activity during sleep

Abstract

Previous study revealed that phase coherence (&lambda) of respiratory sinus arrhythmia (RSA) correlated with parasympathetic nerve activity. The aim of the present study was to examine how &lambda is altered depending on the sleep status and to evaluate the temporal relationship to the brain activity during sleep. Overnight EEG and ECG of 17-healthy volunteers were recorded. The EEG was band-pass filtered to extract the activity in the &delta-range. RSA was determined by applying a band-pass filter to the R-R intervals. From the oscillatory signals of RSA and respiration, time-dependent &lambda was obtained. Using auto- and cross-correlation analyses, we found that the periodicity of &lambda was quite similar to that of &delta-wave and that the variation of &lambda preceded changes in &delta-wave in the order of few minutes. These results suggest that &lambda is coupled with EEG &delta-activity and that &lambda could be used as a measure of sleep status.