title: The role of the spontaneous and evoked k-complex in good-sleeper controls and in individuals with insomnia.
abstract: OBJECTIVE
  Spontaneous and evoked K-complexes are believed to reflect a mechanism of sleep protection, yet their functional role remains a subject of debate. Studying the K-complex in primary insomnia, for which sleep protection appears to be of central importance, may provide further insight on its role. The purpose of the present study was to determine the role of spontaneous and evoked K-complexes in good sleepers and to investigate its role in primary insomnia.
  
  
  METHODS
  Twelve individuals with primary insomnia (mean age = 45.4 years) and 12 good-sleeper controls (mean age = 44.3 years).
  
  
  METHODS
  Participants underwent 4 consecutive nights of polysomnographic recordings. Spontaneous K-complexes (SKC) were analyzed during continuous stage 2 sleep on the third night, whereas evoked K-complexes (EKC) were elicited by auditory stimuli on the fourth night. Relative spectral power was measured on 1-second electroencephalographic segments prior to and following SKC, EKC, and trials in which auditory stimuli did not elicit a K-complex (EKC-). K-complex amplitudes were also measured.
  
  
  RESULTS
  Measures of relative spectral power showed significant changes following EKC (increase in activity in the delta frequency band and decrease in activity in the theta, sigma, beta, and gamma frequency bands) and SKC (increase in activity in delta frequency band and decrease in activity in theta, alpha, sigma, and beta frequency bands) for good sleepers, whereas there was no such marked change in electroencephalographic activity surrounding EKC-. A similar pattern of electroencephalographic activity was also observed for the insomnia group on trials of each different K-complex. Auditory stimuli elicited the same proportion of EKC for both groups, whereas SKC density was higher for the insomnia group (1.52 SKC/min) than for good sleepers (1.06 SKC/minute)
  
  
  CONCLUSIONS
  These results suggest that the SKC and the EKC both promote deeper sleep, further supporting a sleep-protection role.
authors: École de psychologie, Université Laval, Québec, Canada.
authors: Daniel
authors: D
authors: Forget
authors: Charles M
authors: CM
authors: Morin
authors: Clyne H
authors: CH
authors: Bastien
mesh_terms: D000328:Adult; D001143:Arousal / Q000502:physiology; D001307:Auditory Perception / Q000502:physiology*; D016022:Case-Control Studies; D004569:Electroencephalography; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017286:Polysomnography; D007319:Sleep Initiation and Maintenance Disorders / Q000503:physiopathology*; D012894:Sleep Stages / Q000502:physiology*