Neural processes associated with antisaccade task performance investigated with event-related FMRI.

ABSTRACT

One of the hallmarks of cognitive control is the suppression of prepotent but inappropriate responses. Here we used event-related functional MRI to measure functional brain activation during a stimulus-response incompatibility task. Subjects were instructed before a stimulus appeared either to look at the stimulus (prosaccade) or to look away from the stimulus (antisaccade). Eye movements were recorded so that functional brain activation could be grouped into prosaccades, correct antisaccades, and errors (saccades toward the stimulus on antisaccade trials). Correct antisaccade trials were associated with significantly more activation in frontal and parietal cortical areas compared with prosaccade trials during the late preparatory period before stimulus appearance. Correct antisaccades evoked more activation than errors in the right dorsolateral prefrontal cortex, anterior cingulate cortex (ACC), and presupplementary eye fields during this period. No significant differences were found for any comparisons early in the preparatory period. Our data suggest that the preparation of an antisaccade activates a large frontal and parietal network that may be involved in presetting the oculomotor system for the antisaccade task. These findings indicate that a large network of frontal and posterior areas is modulated during the latter component of the preparatory period on antisaccade compared with prosaccade trials. The results further suggest that the activation level of frontal cortical areas before stimulus presentation is associated with subjects' performance in the antisaccade task. In contrast, we found no areas that were more active for correct antisaccades than prosaccades or for correct antisaccades than error antisaccades during the stimulus-response period. In fact, a number of posterior cortical areas and a few areas in the superior frontal lobe were more active during the stimulus-response period on prosaccade trials than on antisaccade trials. Error antisaccades showed a larger activation in the ACC during the stimulus-response period compared with correct antisaccades.