title: Motivation modulates the P300 amplitude during brain-computer interface use.
abstract: OBJECTIVE
  This study examined the effect of motivation as a possible psychological influencing variable on P300 amplitude and performance in a brain-computer interface (BCI) controlled by event-related potentials (ERP).
  
  
  METHODS
  Participants were instructed to copy spell a sentence by attending to cells of a randomly flashing 7*7 matrix. Motivation was manipulated by monetary reward. In two experimental groups participants received 25 (N=11) or 50 (N=11) Euro cent for each correctly selected character; the control group (N=11) was not rewarded. BCI performance was defined as the overall percentage of correctly selected characters (correct response rate=CRR).
  
  
  RESULTS
  Participants performed at an average of 99%. At electrode location Cz the P300 amplitude was positively correlated to self-rated motivation. The P300 amplitude of the most motivated participants was significantly higher than that of the least motivated participants. Highly motivated participants were able to communicate correctly faster with the ERP-BCI than less motivated participants.
  
  
  CONCLUSIONS
  Motivation modulates the P300 amplitude in an ERP-BCI.
  
  
  CONCLUSIONS
  Motivation may contribute to variance in BCI performance and should be monitored in BCI settings.
authors.affiliation: Institute of Medical Psychology and Behavioural Neurobiology, University of Tübingen, Tübingen, Germany. sonja.kleih@medizin.uni-tuebingen.de
authors.forename: S C
authors.initials: SC
authors.lastname: Kleih
authors.forename: F
authors.initials: F
authors.lastname: Nijboer
authors.forename: S
authors.initials: S
authors.lastname: Halder
authors.forename: A
authors.initials: A
authors.lastname: Kübler
mesh_terms: D000328:Adult; D001921:Brain / Q000502:physiology*; D018913:Event-Related Potentials, P300 / Q000502:physiology*; D006801:Humans; D009042:Motivation / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods; D011597:Psychomotor Performance / Q000502:physiology; D011930:Reaction Time / Q000502:physiology; D014584:User-Computer Interface