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Abstract:
Individuals with cerebellar lesions are impaired on a variety
of tasks that require precise timing such as repetitive finger
tapping and duration perception. At this meeting last year
(Spencer, Ivry, & Zelaznik), we presented evidence that
temporal control of continuous tasks (e.g., circle drawing) may not
involve the same timing processes as those involved in
non-continuous tasks (e.g., tapping). In the present study, we
compared the effects of cerebellar lesions on the timing of
continuous and non-continuous motor tasks. Six individuals with
unilateral lesions of the cerebellum were tested on a continuous
circle drawing task and two discrete tasks, finger tapping and
intermittent circle drawing. Temporal variability was significantly
greater with the impaired limb compared to the unimpaired limb on
the non-continuous movement tasks. In contrast, performance for the
two limbs was comparable on the continuous circle drawing task.
This dissociation provides further support that different processes
are involved in timing continuous and non-continuous movements. The
importance of the cerebellum in the latter type of movement may
reflect the need for an explicit representation of the temporal
goal and/or the increased need for processes involved in starting
and stopping movements.
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