Journal Article

Canceling Planned Action: An fMRI Study of Countermanding Saccades

Clayton E. Curtis, Michael W. Cole, Vikas Y. Rao and Mark D'Esposito

in Cerebral Cortex

Volume 15, issue 9, pages 1281-1289
Published in print September 2005 | ISSN: 1047-3211
Published online December 2004 | e-ISSN: 1460-2199 | DOI: http://dx.doi.org/10.1093/cercor/bhi011
Canceling Planned Action: An fMRI Study of Countermanding Saccades

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We investigated the voluntary control of motor behavior by studying the process of deciding whether or not to execute a movement. We imaged the human dorsal cortex while subjects performed a countermanding task that allowed us to manipulate the probability that subjects would be able to cancel a planned saccade in response to an imperative stop signal. We modeled the behavioral data as a race between gaze-shifting mechanisms and gaze-holding mechanisms towards a finish line where a saccade is generated or canceled, and estimated that saccade cancelation took ∼160 ms. The frontal eye fields showed greater activation on stop signal trials regardless of successful cancelation, suggesting coactivation of saccade and fixation mechanisms. The supplementary eye fields, however, distinguished between successful and unsuccessful cancelation, suggesting a role in monitoring performance. These oculomotor regions play distinct roles in the decision processes mediating saccadic choice.

Keywords: countermanding; eye fields; fMRI; inhibition; monitoring; oculomotor; saccades

Journal Article.  8010 words.  Illustrated.

Subjects: Neuroscience

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