Abstract

Antisaccade task performance relies on one's ability to suppress a reflexive, sensory guided saccade made toward a cue in favor of a volitional saccade made away from a cue. Previous studies have implicated a fronto-parietal circuit in the inhibition of reflexive saccades. However, these studies have employed blocked designs which lack the requisite temporal resolution to capture this inhibitory process which is brief in duration compared to other task demands such as prolonged fixation and the generation of saccades. Previous studies have also neglected differences in mental set that exist between prosaccade and antisaccade blocks of trials. The current study used an interleaved antisaccade paradigm optimized for event-related fMRI. At the beginning of a trial, subjects were given an instruction that called for a prosaccade, antisaccade, or no-saccade on the occurrence of a suddenly appearing peripheral cue. Real-time monitoring of eye movements allowed us to relate fMRI data with performance. Analyses focused on the different neural contributions to motor preparation, monitoring, and saccade initiation/suppression. Frontal and supplementary eye fields (SEF) and the posterior parietal cortex were all more active during antisaccade trials. This pattern was limited to the response portion of the task. The SEF showed greater activity prior to the response on trials in which a reflexive saccade was withheld, possibly reflecting monitoring or preparation. The results suggest different roles for dorsal frontal and parietal regions during performance of antisaccade tasks, and help clarify general mechanisms of performance monitoring and inhibitory control.

From: Curtis, C. E. and M. D'Esposito (2001). Differential contributions from dorsal frontal cortical regions in inhibitory control: fMRI evidence from an antisaccade task. Society for Neuroscience, San Diego.