title: Prestimulus vigilance predicts response speed in an easy visual discrimination task.
abstract: BACKGROUND
  Healthy adults show considerable within-subject variation of reaction time (RT) when performing cognitive tests. So far, the neurophysiological correlates of these inconsistencies have not yet been investigated sufficiently. In particular, studies rarely have focused on alterations of prestimulus EEG-vigilance as a factor which possibly influences the outcome of cognitive tests. We hypothesised that a low EEG-vigilance state immediately before a reaction task would entail a longer RT. Shorter RTs were expected for a high EEG-vigilance state.
  
  
  METHODS
  24 female students performed an easy visual discrimination task while an electroencephalogram (EEG) was recorded. The vigilance stages of 1-sec-EEG-segments before stimulus presentation were classified automatically using the computer-based Vigilance Algorithm Leipzig (VIGALL). The mean RTs of each EEG-vigilance stage were calculated for each subject. A paired t-test for the EEG-vigilance main stage analysis (A vs. B) and a variance analysis for repeated measures for the EEG-vigilance sub-stage analysis (A1, A2, A3, B1, B2/3) were calculated.
  
  
  RESULTS
  Individual mean RT was significantly shorter for events following the high EEG-vigilance stage A compared to the lower EEG-vigilance stage B. The main effect of the sub-stage analysis was marginal significant. A trend of gradually increasing RT was observable within the EEG-vigilance stage A.
  
  
  CONCLUSIONS
  We conclude that an automatically classified low EEG-vigilance level is associated with an increased RT. Thus, intra-individual variances in cognitive test might be explainable in parts by the individual state of EEG-vigilance. Therefore, the accuracy of neuro-cognitive investigations might be improvable by simultaneously controlling for vigilance shifts using the EEG and VIGALL.
authors.affiliation: Department of Psychiatry and Psychotherapy, University of Leipzig, Semmelweisstr, 10, 04103 Leipzig, Germany.
authors.forename: Juliane
authors.initials: J
authors.lastname: Minkwitz
authors.forename: Maja U
authors.initials: MU
authors.lastname: Trenner
authors.forename: Christian
authors.initials: C
authors.lastname: Sander
authors.forename: Sebastian
authors.initials: S
authors.lastname: Olbrich
authors.forename: Abigail J
authors.initials: AJ
authors.lastname: Sheldrick
authors.forename: Peter
authors.initials: P
authors.lastname: Schönknecht
authors.forename: Ulrich
authors.initials: U
authors.lastname: Hegerl
authors.forename: Hubertus
authors.initials: H
authors.lastname: Himmerich
mesh_terms: D000328:Adult; D001143:Arousal / Q000502:physiology*; D004193:Discrimination Learning / Q000502:physiology*; D004569:Electroencephalography / Q000379:methods*; D005260:Female; D005544:Forecasting; D006801:Humans; D010775:Photic Stimulation / Q000379:methods; D011597:Psychomotor Performance / Q000502:physiology; D011930:Reaction Time / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult