title: Diurnal variation in the quantitative EEG in healthy adult volunteers.
abstract: OBJECTIVE
  To define the change in power in standard waveband frequencies of quantitative cortical electroencephalogram (EEG) data over a 24 h period, in a drug free representative healthy volunteer population.
  
  
  METHODS
  This was an open, non randomised study in which 18 volunteers (9 male and 9 female) were studied on 1 study day, over a 24 h period. Volunteers had a cortical EEG recording taken at 0, 2, 4, 6, 8, 10, 12, 16 and 24 h. Each recording lasted for 6 min (3 min eyes open, 3 min eyes closed). All EEG recordings were taken in a quietened ward environment with the curtains drawn round the bed and the volunteer supine. During the 3 min eyes open, volunteers were asked to look at a red circle on a screen at the foot of the bed, and refrain from talking.
  
  
  RESULTS
  Plots produced of geometric mean power by time of the standard wave band frequencies gave some indication of a circadian rhythm over the 24 h period for theta (4. 75-6.75 Hz), alpha1 (7.0-9.5 Hz) and beta1 (12.75-18.50 Hz) wavebands. Mixed models were fitted to both the eyes open and eyes closed data which confirmed a change in mean waveband power with time with statistical significance at the conventional 5% level (P < 0.05).
  
  
  CONCLUSIONS
  These data indicate the presence of a diurnal variation in the cortical quantitative EEG. They support the use of a placebo control group when designing clinical trials which utilize quantitative EEG to screen for central nervous system (CNS) activity of pharmaceutical agents, to control for the confounding variable of time of day at which the EEG recordings were made.
authors.affiliation: Clinical Pharmacology Unit, Zeneca Pharmaceuticals, Mereside, Alderley Park, Macclesfield, Cheshire, UK.
authors.forename: L
authors.initials: L
authors.lastname: Cummings
authors.forename: A
authors.initials: A
authors.lastname: Dane
authors.forename: J
authors.initials: J
authors.lastname: Rhodes
authors.forename: P
authors.initials: P
authors.lastname: Lynch
authors.forename: A M
authors.initials: AM
authors.lastname: Hughes
mesh_terms: D000328:Adult; D001921:Brain / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology*; D004569:Electroencephalography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged