K-Complexes: Interaction Between the Central and Autonomic Nervous Systems During Sleep

Sleep. 2016 May 1;39(5):1129-37. doi: 10.5665/sleep.5770.


Study objectives: To investigate the relationship between K-complexes (KCs) and cardiac functioning.

Methods: Forty healthy adolescents aged 16-22 y (19 females) participated in the study. Heart rate (HR) fluctuations associated with spontaneous and evoked KCs were investigated on two nights, one with (event-related potential night) and one without auditory tones presented across the night.

Results: There was a clear biphasic cardiac response to evoked and spontaneous KCs, with an initial acceleration in HR followed by a deceleration (P < 0.001). HR acceleration occurred immediately to KCs in response to tones presented in the first third of the interbeat interval, but was delayed a beat when the tone occurred later in the cardiac cycle (P < 0.05). Sex differences were also evident. Pretone baseline HR was higher, and the magnitude of the HR response was blunted and delayed, in female compared to male adolescents (P < 0.001). Also, pretone baseline HR was lower when a tone elicited a KC compared to when it did not (P < 0.001), suggesting that KCs are possibly more likely to be elicited by external stimuli in states of reduced cardiac activation.

Conclusions: The strict dependency observed between KCs and cardiac control indicates a potential role of KCs in modulating the cardiovascular system during sleep. Sex differences in the KC-cardiac response indicate the sensitivity of this measure in capturing sex differences in cardiac regulatory physiology.

Keywords: K-complex; autonomic nervous system; cardiovascular; heart rate; sex differences; sleep.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Acoustic Stimulation
  • Adolescent
  • Autonomic Nervous System / physiology*
  • Central Nervous System / physiology*
  • Electroencephalography*
  • Evoked Potentials
  • Female
  • Healthy Volunteers
  • Heart Rate / physiology*
  • Humans
  • Male
  • Sex Characteristics
  • Sleep / physiology*
  • Sleep Stages / physiology
  • Young Adult