J Neurol Neurosurg Psychiatry 1998;65:328-337 ( September )
Motor switching abilities in Parkinson's disease and old age:
temporal aspects
Meir Plotnik,a b
Tamar Flash,b
Rivka Inzelberg,b c
Edna Schechtman,d
Amos D Korczyna c
a Sreratzki Chair of
Neurology, Tel-Aviv University, Tel-Aviv, Israel, b Department of Applied
Mathematics and Computer Science, the Weizmann Institute of Science,
Rehovot, Israel, c Department of Neurology, Tel-Aviv Sourasky
Medical Center, Tel-Aviv, Israel, d Computer
Center, the Weizmann Institute of Science, Rehovot, Israel
Correspondence to: Dr Amos D Korczyn,
Department of Neurology, Sackler Faculty of Medicine, Tel-Aviv
University, Ramat-Aviv, 69978, Israel.
Received 20 December
1996 and in revised form 26 November 1997;
Accepted 16 February
1998
OBJECTIVES
To
investigate capabilities of arm trajectory modification in patients
with Parkinson's disease and elderly subjects using a double step
target displacement paradigm.
METHODSNine patients
with Parkinson's disease and seven age matched control subjects were
instructed to move a stylus towards visual targets presented on a
digitising table. Within each session, in some trials the target
location was changed before initiation of movement and the subjects
were to modify their movements towards the new target (switching
trials). In other trials the target location was not changed (control
trials). This procedure was repeated for four different target
configurations, using interstimulus time intervals of six different
durations. The subjects' hand trajectories were recorded and their
kinematic characteristics were analysed.
RESULTSIn switching
trials, about 40% of the movements were aimed directly toward the
final target location in both groups. When the trajectories were
initially directed toward the first target and then modified toward the
second, the reaction time (RT) to the second stimulus (RT2)
was longer than to the first stimulus (RT1). The
RT2/RT1 ratio was significantly larger in
patients with Parkinson's disease than in healthy elderly subjects.
CONCLUSIONSPatients
with Parkinson's disease and elderly subjects are substantially slower
in responding to a required modification of their movement than in
responding to the required movement initiation. Patients with
Parkinson's disease have impaired capabilities in processing
simultaneously the motor responses to two visual stimuli presented in
rapid succession.
Keywords:
Parkinson's disease;
motor switching;
basal
ganglia;
kinematics
© 1998 by Journal of Neurology, Neurosurgery, and Psychiatry
