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Abstract:
Abstract: The cerebral correlates of timing processes were
investigated using rhythmical coordinated eye movements (saccades)
during fMRI (12 subjects). Two tasks were presented visually in
randomized order and announced by verbal cues. In both tasks,
subjects had to fixate the currently marked item of eight circles
arranged in two horizontal rows. In the rhythm task R, variations
of the first four marking times presented a short rhythm. This
four-piece rhythm was presented four times in both the learning and
the test phase in each trial. The subject had to indicate changes
in the rhythm (deviants) by button presses (task R), and visually
different items (targets) in the control task C, respectively.
During the experiment echo planar images were acquired from 16
axial slices. Pure motor, perceptual and attentional effects were
substracted out by the C condition. As in former timing studies,
structures found to be bilaterally activated only during the rhythm
task were the supplementary motor area (SMA), the premo-tor cortex
(PMC), the lateral cerebellar cortex, the basal ganglia, and the
pars opercularis (BA 44). As expected, the frontal eye field (FEF)
was activated, but only in the right hemisphere. Moreover, there
was a marked activation dominance for the left hemisphere during
the learn-ing phase and for the right hemisphere during the test
phase, suggesting hemispheric preferences either for different
processes (encoding/left vs. recall/right) or for different
information formats (local, single elements/left vs. global,
grouped information/right).
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