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for both flexion and extension movements in the MPTP-treated and electrolytical le-
sioned animals. Weiss et al. [52] investigated the kinematic organization of discrete
elbow movements of different amplitudes to targets of various sizes of young, el-
derly, and PD subjects. The investigators reported a significant increase in the simple
reaction time between young, elderly, and PD subjects over all conditions.
11.5.5 Repetitive Triphasic Pattern of Muscle Activation
Hallett and Khoshbin [37] asked healthy and Parkinson's disease (PD) patients
to make rapid accurate elbow flexion movements of different angular distances
(10, 20, and 40) while they recorded their EMG activities and their elbow angles
with surface electrodes. They reported that healthy subjects exhibited a tripha-
sic (agonist-antagonist-agonist) EMG pattern. However, the EMG patterns in the
muscles of Parkinson's disease patients differed from those of the healthy sub-
jects in that the bursts of EMG activity in the agonist muscle did not increase in
magnitude for the larger amplitude movements. Hallett and Khoshbin [37] inter-
preted their results indicating that patients with PD are unable to sufficiently acti-
vate agonist muscles during movements made as quickly as possible. They showed
that an apparent compensation for the decreased muscular activation was to evoke
more cycles of activity to complete the movement. Doudet et al. [23] reported
that in order for MPTP-treated animals to achieve the full amplitude of the re-
quired movement, additional successive bursts of lower amplitude and duration were
needed.
11.5.6 Electromechanical Delay Time Is Increased
Electromechanical delay time (EMT; time between the onset of modification of ag-
onist EMG activity and the onset of movement (OM); see Fig. 11.3) is significantly
increased in MPTP-treated animals. Benazzouz et al. [2] study showed that mon-
keys display a significant increase in the EMD time. Doudet et al. [24, 23] in the
exact same experimental paradigm observed a similar delay in EMT.
11.5.7 Depression of Rate of Development and Peak Amplitude
of the First Agonist Burst of EMG Activity
Godaux and colleagues [34] conducted experiments with control and PD patients
seated facing a target button. Subjects were instructed to switch off the target button
when it lit, by pressing it as rapidly as possible. The activities of anterior deltoid,
biceps brachii, triceps brachii, and extensor indicis muscles were recorded using sur-
