title: Independent contributions of cortical gray matter, aging, sex and alcoholism to K-complex amplitude evoked during sleep.
abstract: OBJECTIVE
  The amplitude of the N550 component derived from the averaged evoked K-complex decreases with normal aging and with alcoholism. The study was designed to determine whether these declines are related to the extent of cortical or subcortical shrinkage.
  
  
  METHODS
  Research sleep laboratory and MR imaging facility
  
  
  METHODS
  26 abstinent long-term alcoholic men, 14 abstinent long-term alcoholic women, 18 control men, and 22 control women.
  
  
  RESULTS
  MRI data collected at 3T were analyzed from alcoholic and control men and women previously reported to have significantly different evoked delta activity during sleep. Segmented and parcellated MRI data collected at 3T were compared between these groups and evaluated for correlation with evoked K-complex amplitude measured at FP1, Fz, FCz, Cz, CPz, and Pz. Cortical gray matter and regional subcortical tissue volumes entered as predictors into stepwise multiple regression identified cortical gray matter as a unique significant predictor of evoked K-complex at all sites. Age added independent variance at 5 of the 6 sites, while alcoholism and sex added independent variance at frontal sites only.
  
  
  CONCLUSIONS
  These data support recent intracranial studies showing cortical generation of K-complexes by indicating that cortical, but not subcortical volume contributes to K-complex amplitude. Establishing the extent of the relation between cortical volume and K-complex amplitude provides a mechanistic understanding of sleep compromise clinically relevant to normal aging, alcoholism, and likely other conditions affecting cortical volume and integrity.
authors.affiliation: Human Sleep Research Program, SRI International, Menlo Park, CA 94025, USA. ian.colrain@sri.com
authors.forename: Ian M
authors.initials: IM
authors.lastname: Colrain
authors.forename: Edith V
authors.initials: EV
authors.lastname: Sullivan
authors.forename: Torsten
authors.initials: T
authors.lastname: Rohlfing
authors.forename: Fiona C
authors.initials: FC
authors.lastname: Baker
authors.forename: Christian L
authors.initials: CL
authors.lastname: Nicholas
authors.forename: Mayra L
authors.initials: ML
authors.lastname: Padilla
authors.forename: Sandra
authors.initials: S
authors.lastname: Chanraud
authors.forename: Anne-Lise
authors.initials: AL
authors.lastname: Pitel
authors.forename: Adolf
authors.initials: A
authors.lastname: Pfefferbaum
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000437:Alcoholism / Q000503:physiopathology*; D016022:Case-Control Studies; D002540:Cerebral Cortex / Q000503:physiopathology*; D003700:Delta Rhythm / Q000502:physiology*; D004569:Electroencephalography; D005071:Evoked Potentials / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012737:Sex Factors; D012890:Sleep / Q000502:physiology*