Prestimulus cortical potentials predict the performance in a saccadic distractor paradigm.
OBJECTIVE
In distractor paradigms, subjects sometimes respond to the wrong stimulus in a reflex-like manner. It is poorly understood why these errors occur.


METHODS
To investigate the cortical processes possibly responsible for these errors, we recorded event-related potentials (ERPs) in human subjects performing a distractor saccade task in which subjects had to select a saccade target based on the colour of the initial fixation point and ignore a distractor on the opposite side. The initial fixation point disappeared 200 ms before the presentation of the visual stimuli (gap period). We compared the ERPs between correct trials in which subjects looked to the correct stimulus with error trials in which they looked towards the wrong stimulus.


RESULTS
Correct response trials and error response trials showed a negative potential at the end of the gap period with the greatest amplitude over the fronto-central cortex. However, this potential had a lower amplitude in error response trials compared to correct response trials.


CONCLUSIONS
These findings suggest that task-specific preparatory cortical processes in the frontal lobe prior to stimulus presentation have a major influence on the performance in distractor paradigms.
Everling
S
S
Departments of Physiology and Psychology, University of Western Ontario, Social Science Centre, London, Ontario N6A 5C2, Canada. severlin@julian.uwo.ca
Matthews
A
A
Flohr
H
H
D000328:Adult; D000704:Analysis of Variance; D002540:Cerebral Cortex / Q000502:physiology*; D005071:Evoked Potentials / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D010775:Photic Stimulation / Q000379:methods; D011930:Reaction Time / Q000502:physiology*; D012438:Saccades / Q000502:physiology*