title: Inverse coupling between ultradian oscillations in delta wave activity and heart rate variability during sleep.
abstract: OBJECTIVE
  We investigate the relationship between changes in heart rate variability and electroencephalographic (EEG) activity during sleep.
  
  
  METHODS
  Nine male subjects with regular non-rapid-eye movement-rapid-eye movement (NREM-REM) sleep cycles were included in the study. They underwent EEG and cardiac recordings during one experimental night. Heart rate variability was determined over 5-min periods by the ratio of low frequency to low frequency plus high frequency power [LF/(LF+HF)] calculated using spectral analysis of R-R intervals. EEG spectra were analyzed using a fast Fourier transform algorithm.
  
  
  RESULTS
  We found an ultradian 80-120 min rhythm in the LF/(LF+HF) ratio, with high levels during rapid eye movement (REM) sleep and low levels during slow wave sleep (SWS). During sleep stage 2 there was a progressive decrease in the transition from REM sleep to SWS, and an abrupt increase from SWS to REM sleep. These oscillations were significantly coupled in a 'mirror-image' to the overnight oscillations in delta wave activity, which reflect sleep deepening and lightening. Cardiac changes preceded EEG changes by about 5 min.
  
  
  CONCLUSIONS
  These findings demonstrate the existence of an inverse coupling between oscillations in delta wave activity and heart rate variability. They indicate a non-uniformity in sleep stage 2 that underlies ultradian sleep regulation.
authors.affiliation: Laboratoire des Régulations Physiologiques et des Rythmes Biologiques chez l'Homme, 4 rue Kirschleger, 67085 Cedex, Strasbourg, France. brandenberger.gabrielle@medecine.u-strasbg.fr
authors.forename: G
authors.initials: G
authors.lastname: Brandenberger
authors.forename: J
authors.initials: J
authors.lastname: Ehrhart
authors.forename: F
authors.initials: F
authors.lastname: Piquard
authors.forename: C
authors.initials: C
authors.lastname: Simon
mesh_terms: D000204:Activity Cycles / Q000502:physiology*; D000328:Adult; D000704:Analysis of Variance; D003700:Delta Rhythm / Q000379:methods; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D012894:Sleep Stages / Q000502:physiology*