The reaching movements of patients with Parkinson's disease under self- determined maximal speed and visually cued conditions

Abstract

Two-dimensional kinematic analysis was performed of the reaching movements that six subjects with Parkinson's disease and six healthy subjects produced under self-determined maximal speed and visually cued conditions. Subjects were required to reach as fast as possible to grasp a ball (i) that was fixed stationary in the centre of a designated contact zone on an inclined ramp (self-determined maximal speed condition), or (ii) that rolled rapidly from left to right down the incline and into the contact zone (visually cued condition). Parkinson's disease subjects displayed bradykinesia when performing maximal speed reaches to the stationary ball, but not when they reached for the moving ball. In response to the external driving stimulus of the moving ball, Parkinson's disease subjects showed the ability to exceed their self-determined maximal speed of reaching and still maintain a movement accuracy that was comparable to that of healthy subjects. Thus, the bradykinesia of Parkinson's disease subjects did not seem to be the result of a basic deficit in their force production capacity or to be a compensatory mechanism for poor movement accuracy. Instead, bradykinesia appeared to result from the inability of Parkinson's disease subjects to maximize their movement speed when required to internally drive their motor output. The occasional failure of Parkinson's disease subjects to successfully grasp the moving ball suggested errors of coincident anticipation and impairments in grasp performance rather than limitations in the speed or accuracy of their reaches. These results are discussed in relation to the notion that the motor circuits of the basal ganglia play an important role in the modulation of internally regulated movements.

Control of aperture closure during reach-to-grasp movements in parkinson’s disease

“…Means standard errors, and F values of the kinematic measures are shown in Table 2. In agreement with numerous studies that reported bradykinetic movements in PD patients (Alberts et al 2000;Castiello et al 1999;Majsak et al 1998;Tresilian et al 1997), the PD patients produced significantly slower transport movements than controls (P<0.05). As for the grasp component, PD group had a significantly smaller amplitude of maximum grip aperture than controls (P<0.001), showing the hypometric movement features that are typical for individuals with PD (Castiello and Bennett 1994;Castiello et al 1999;Gentilucci and Negrotti 1999).…”

“…Since the PD patients exhibited a smaller grip aperture and moved their hand significantly more slowly than the control subjects, the control law predicts that the distance to target at which they initiated aperture closure should also be shorter. Thus, the shorter aperture closure distance observed in PD patients can be viewed as resulting from hypometria of their grip aperture (Castiello and Bennett 1994;Castiello et al 1999;Gentilucci and Negrotti 1999) and bradykinesia of their hand transport (Alberts et al 2000;Castiello et al 1999;Majsak et al 1998;Tresilian et al 1997), rather than being a result of a deficit in transport-grip coordination in terms of the initiation of aperture closure.…”

Dopaminergic contributions to distance estimation in Parkinson's disease: A sensory-perceptual deficit?

“…The current study was able to rule out this hypothesis by testing participants in a passive motion condition (i.e., pushed in a wheelchair) as well as in virtual reality where visual motion was simulated without vestibular information. During passive motion (wheelchair condition), both groups did not differ in judgment accuracy demonstrating that when all other sensory cues are available, and proprioception is limited, PD patients are able to estimate distance with motion as accurately as healthy control 30 participants suggesting perhaps that visual motion stimuli engage neural circuits that are less affected by PD (Majsak, Kaminski, Gentile, & Flanagan, 1998;Majsak, Kaminski, Gentile, & Gordon, 2008).…”

Levodopa improves time-based prospective memory in Parkinson's disease

“…It occurs, for example, when a patient with symptoms of akinesia and bradykinesia responds to an alarm by walking rapidly away from the scene. Several studies support these clinical observations, documenting that the ability of patients with PD to begin a motor sequence is more severely impaired (in terms of response times) when they have to rely on self-determined mechanisms than when the drive to act is triggered by an external cue (Jahanshahi et al, 1995;Majsak et al, 1998;Siegert et al, 2002). Overall, these findings are fairly consistent with our finding of a selective impairment after L-dopa withdrawal in the component of the task that specifically requires the subject to self-activate the intention to perform the actions.…”

“…A parallel could be drawn between the deficit in self initiating the prospective intention and the phenomenon of "akinesia paradoxica" held to be characteristic of PD (Jahanshahi et al, 1995;Majsak et al, 1998;Siegert et al, 2002; but see Ballanger et al, 2006, for partially divergent view). This term refers to the fact that PD patients can often initiate movements more quickly in response to external stimuli than voluntarily.…”