title: Circadian course of the P300 ERP in patients with amyotrophic lateral sclerosis - implications for brain-computer interfaces (BCI).
abstract: BACKGROUND
  Accidents or neurodegenerative diseases like amyotrophic lateral sclerosis (ALS) can lead to progressing, extensive, and complete paralysis leaving patients aware but unable to communicate (locked-in state). Brain-computer interfaces (BCI) based on electroencephalography represent an important approach to establish communication with these patients. The most common BCI for communication rely on the P300, a positive deflection arising in response to rare events. To foster broader application of BCIs for restoring lost function, also for end-users with impaired vision, we explored whether there were specific time windows during the day in which a P300 driven BCI should be preferably applied.
  
  
  METHODS
  The present study investigated the influence of time of the day and modality (visual vs. auditory) on P300 amplitude and latency. A sample of 14 patients (end-users) with ALS and 14 healthy age matched volunteers participated in the study and P300 event-related potentials (ERP) were recorded at four different times (10, 12 am, 2, & 4 pm) during the day.
  
  
  RESULTS
  Results indicated no differences in P300 amplitudes or latencies between groups (ALS patients v. healthy participants) or time of measurement. In the auditory condition, latencies were shorter and amplitudes smaller as compared to the visual condition.
  
  
  CONCLUSIONS
  Our findings suggest applicability of EEG/BCI sessions in patients with ALS throughout normal waking hours. Future studies using actual BCI systems are needed to generalize these findings with regard to BCI effectiveness/efficiency and other times of day.
authors.affiliation: Institute of Psychology, University of Würzburg, Würzburg, Germany.
authors.forename: Helena
authors.initials: H
authors.lastname: Erlbeck
authors.affiliation: Institute of Medical Psychology, University of Tübingen, Tübingen, Germany.
authors.forename: Ursula
authors.initials: U
authors.lastname: Mochty
authors.affiliation: Institute of Psychology, University of Würzburg, Würzburg, Germany.
authors.forename: Andrea
authors.initials: A
authors.lastname: Kübler
authors.affiliation: Institute of Psychology, University of Würzburg, Würzburg, Germany. ruben.real@med.uni-goettingen.de.|Institute of Medical Psychology and Medical Sociology, University Medical Center Göttingen, Waldweg 37, 37073, Göttingen, Germany. ruben.real@med.uni-goettingen.de.
authors.forename: Ruben G L
authors.initials: RG
authors.lastname: Real
mesh_terms: D000328:Adult; D000690:Amyotrophic Lateral Sclerosis / Q000503:physiopathology*; D062207:Brain-Computer Interfaces; D004569:Electroencephalography / Q000379:methods; D018913:Event-Related Potentials, P300 / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged
keywords: ALS; Amyotrophic Lateral Sclerosis; Auditory; BCI; Brain computer interface; P300; Visual