P300 and response selection: a new look using independent-components analysis.
OBJECTIVE
The most prevalent current view of the functional role of the P300 component of the event-related potential (ERP) is that it indexes strategic processing related to context updating. Using independent-components analysis (ICA), the present study examined the role of P300 in the tactical process of response selection.


METHODS
In a task crossing manipulations of perceptual difficulty (PD) and response-selection difficulty (R-SD), ICA was employed to measure not only P300 latency, but its onset and duration as well.


RESULTS
Increased PD delayed P300 latency and onset in parallel, while increased R-SD lengthened P300 duration.


CONCLUSIONS
The latency and onset results suggest that the often-cited covariation of P300 latency with stimulus-evaluation time is secondary to effects on processing stages preceding P300. The results for duration indicate that P300 is involved in response selection, suggesting that it is not a unitary phenomenon. While P300's well-known relation to stimulus probability indicates a strategic role, our findings indicate a tactical role as well.
Pritchard
W S
WS
Research and Development, R.J. Reynolds Tobacco Company, Winston-Salem, NC 27102, USA. pritchw@rjrt.com
Houlihan
M E
ME
Robinson
J H
JH
D000328:Adult; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000502:physiology*; D018913:Event-Related Potentials, P300 / Q000502:physiology*; D006801:Humans; D008297:Male; D016571:Neural Networks, Computer; D011597:Psychomotor Performance / Q000502:physiology; D011930:Reaction Time / Q000502:physiology