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Abstract:
We have previously shown that regular and irregular SI finger
movements activate a fronto-striatal 'willed action system'. The
aim of this study was to examine (i) the cross-effector generality
of a willed action system by investigating volitionally timed
saccades (ii) the functional anatomy of stimulus anticipation/motor
preparation by comparing regular vs irregular sacccades with PET
and MRPs recorded concurrently. We used a 3 Conditions (SI, ET,
tone alone) x 2 Rate (regular vs irregular) factorial design.
Compared to the control tone condition, the SI and ET saccades
activated fronto-striatal areas and cerebellum. SI saccades
activated the left anterior cingulate more than ET saccades.
Regular saccades activated the right anterior cingulate and left
middle temporal gyrus more than regular saccades. The amplitude and
slope of MRPs were highest prior to irregular SI saccades, followed
by the regular SI and regular ET conditions. The results (i)
confirm the cross-effector generality of a fronto-striatal willed
action system with the anterior cingulate being a key component
(ii) suggest that development of MRPs are related to the
decision-making, stimulus anticipation/motor preparation that were
respectively possible in the SI and regular ET conditions, but not
the irregular ET condition.
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