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Cereb Cortex. 2005 Sep;15(9):1281-9. Epub 2004 Dec 22.

Canceling planned action: an FMRI study of countermanding saccades.

Author information

1
New York University, Department of Psychology and Center for Neural Science, New York, NY 10003, USA. clayton.curtis@nyu.edu

Abstract

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 approximately 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.

PMID:
15616130
DOI:
10.1093/cercor/bhi011
[Indexed for MEDLINE]

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