Multichannel Complexity Index Analysis for Cardiovascular Dynamics associated with a Dream Recall

This study reports on a multivariate complexity assessment for cardiovascular dynamics during REM sleep leading to a dream recall. Heart rate variability, as well as systolic and diastolic time interval variability series were gathered from eight volunteers during night sleep, and were considered input of a trivariate Multichannel Complexity Index (MCI) analysis. MCI is a recently proposed index based on a multivariate phase space reconstruction accounting for the intrinsic nonlinearity of the autonomic nervous system dynamics. Results show a significant MCI decrease during REM sleep epochs followed by a dream recall as compared to those associated with no dream recall (p < 10−18). This implies a lower interplay between complex cardiovascular subcomponents during dreaming, complementing current psychophysiological correlates of sleep.