Performance of a bimanual load-lifting task by parkinsonian patients.

Abstract

SUMMARY Normal subjects and Parkinsonian patients performed a bimanual load lifting task. In this task, one "postural" forearm, held in a horizontal position while supporting a 1 kg weight, was unloaded either by the experimenter's hand (imposed unloading) or by the subject's other hand in response to a tone burst (voluntary unloading). The variables recorded were reaction time (RT: time interval between the tone and beginning of unloading) and movement time (MT: duration of the change in force measured by a force platform on the "postural" forearm). Elbow angle changes were also measured with a potentiometer. The EMG activity from brachioradialis of the "postural" arm and that from the biceps of the "active" arm were recorded. The Parkinsonian patients showed an increase in both RT and MT and an impairment of the co-ordination between movement and posture which was reflected in an increase in amplitude of the elbow rotation after voluntary unloading. Moreover, the decrease in EMG activity in the brachioradialis of the postural arm during unloading was less in Parkinsonian patients than in the normal group. This disorder of postural command was often accompanied by a lack of anticipatory EMG changes. Comparison between treated and non-treated patients showed that dopamine agonists brought about recovery of both RT and MT but did not improve postural co-ordination. The co-ordination was less impaired when the voluntary unloading was performed by the preferred hand. Several hypotheses are discussed concerning the mechanism underlying this impaired co-ordination.Performance of a voluntary movement by one body segment is usually accompanied by an adjustment of posture aimed at preventing the imbalance which would otherwise occur.1 Posture and movement have been shown to be co-ordinated in several situations. Under near-static conditions, for instance, Babinski2 observed that backward bending of the body is accompanied by flexion of the knees, restricting displacement of the vertical projection of the centre of gravity to within the area delimited by the feet on the ground. Similarly, raising of the arms forwards leads to a compensatory backward displacement of the trunk.3 Under dynamic conditions, when the voluntary movement is a fast one, the postural adjustment command usually precedes the actual movement. An

Proceedings of the 9th Conference of the Australasian Society for Cognitive Science

“…For the purpose of comparing our results with findings from previous studies, the first EMG burst in the unloading arm was used as the onset of unloading. This is in agreement with previous studies that show the mean movement time to lift a 1-kg weight completely off a force-sensing device is about 200 ms (Viallet et al, 1987(Viallet et al, , 1992 and that the onsets of EMG activity in the unloading arm occurred quasisynchronously with the instance of transient load change (Massion, Ioffe, Schmitz, Vialett, & Gantcheva, 1999;Forget & Lamarre, 1989;Massion et al, 1998). However, the same shift would be inappropriate for the imposed condition because the latency of the unloading reflex in the arm is in the order of 50 ms (Hugon et al, 1987;Schmitz et al, 2002;Forget & Lamarre, 1989).…”

“…Apart from cortical lesions, pathology of subcortical structures including basal ganglia also affects postural adjustment in goal-directed movements. In two studies of patients with Parkinson's disease, the APA was partially preserved in half the patient group and abolished in the rest (Traub, Rothwell, & Marsden, 1980;Viallet, Massion, Massarino, & Khalil, 1987). In another study of patients with cerebellar pathology, APA was found to be largely intact, albeit with an onset significantly earlier relative to normal controls (Diedrichsen, Verstynen, Lehman, & Ivry, 2005).…”

Intended rather than actual movement velocity determines the latency of anticipatory postural adjustments

“…Severe APA impairments in patients with Parkinson's disease suggested a role of the basal ganglia in the anticipatory postural control (Viallet et al 1987). In particular, beyond their role in shaping the movement, basal ganglia may be involved in the intentional movement selection, through the pathway involving the anterior mid-circulates cortex (see Hoffstaedter et al 2013).…”

The emergence and disappearance of multi-digit synergies during force-production tasks

“…Preparation for an action is of a major importance for various everyday actions. It has been shown to suffer in certain neurological conditions such as Parkinson's disease (Bazalgette et al 1986;Viallet et al 1987) and during normal aging (Woollacott et al 1988). We believe that studies of anticipatory covariation in different subpopulations can reveal changes that may be causally related to impairments in motor synergies.…”