Brain, Vol 120, Issue 11 2093-2111, Copyright © 1997 by Oxford University Press
JR Tresilian, GE Stelmach and CH Adler
The performance of patients with Parkinson's disease on two reach-to- grasp
tasks was compared with that of age-matched control subjects. The aim of
the study was to determine whether Parkinson's disease patients have
problems coordinating concurrently executed tasks within the same system of
effectors in a natural context and whether such problems would be
exacerbated by increases in task difficulty. We examined how subjects
concurrently executed the transport and grasp components of reach-to-grasp
movements in the presence of two types of change in task demands: (i)
increases in demands for accurate digit pad placement and (ii) use of two
reach-to-grasp tasks, i.e. the standard unimanual task and a bimanual task
which increased the control and coordination demands relative to the
unimanual task. If Parkinson's disease patients have coordination problems
they should demonstrate increased impairment with increasing accuracy
demands and in the bimanual task; any such differences should be absent or
much smaller in the control group. The Parkinson's disease group showed
substantial impairments in all conditions, moving about 30% slower than the
control group, with much increased jerking and with signs of difficulty
controlling the speed of movement. However, there were no consistent
indications that the Parkinson's disease group were differentially impaired
on the bimanual task nor that movement deficits increased with increasing
accuracy requirements. Grasp and transport components were coordinated
similarly by Parkinson's disease and control groups in both reach-to-grasp
tasks, and the Parkinson's disease group co-ordinated the two limbs in the
bimanual task effectively and in a fashion similar to that of the control
group. These results are interpreted to mean that higher levels
(effector-independent levels) of motor programming are preserved in
Parkinson's disease and that execution of a motor programme need not be
compromised by increasing the number of muscle-/joint-level degrees of
freedom which are used.
ARTICLES
Stability of reach-to-grasp movement patterns in Parkinson's disease
Motor Control Laboratory, Arizona State University, Tempe 85287-0404, USA.
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