Interjoint coordination during pointing movements is disrupted in spastic hemiparesis

Abstract

Approaches to the rehabilitation of movement in spastic hemiparetic patients depend on knowledge of the underlying mechanisms of movement deficits. The goals of this study were to characterize end-point trajectories and interjoint coordination of arm pointing movements to different targets on a horizontal planar surface and to correlate disruptions in motor control in the affected arm of hemiparetic subjects with the level of spasticity and the degree of functional impairment measured clinically. Arm movements were studied in six normal and 10 hemiparetic subjects. Data from the affected arms of hemiparetic subjects were compared with those from their non-affected arms and to data from the arms of normal subjects. Subjects were seated in front of a horizontal surface adjusted to the height of the sternal notch with the trunk stabilized. They made planar arm reaching movements (20 and 40 cm) to four different targets located directly in front of them and in the ipsilateral and contralateral workspace. Kinematic data from the finger, wrist, elbow and shoulder were recorded with a three-dimensional optical tracking system. Results showed that movement amplitudes were lower and movement times were significantly prolonged in the affected arms. Although trajectories were marked by deviations from smooth straight lines and characterized by increased dispersion and segmentation, even those subjects with the most severe spasticity could reach into all parts of the workspace with both their affected and non-affected arms. This indicated that movement planning in terms of extrapersonal space was unaffected in these subjects. On the other hand, the interjoint coordination of movements made into or out of the typical extensor or flexor synergies was equally disrupted. These findings suggest a bi-level control organization of pointing movements in both normal and hemiparetic subjects: the level of trajectory planning in extrapersonal space and the level specifying interjoint coordination according to the trajectory plan. Deficits in motor performance in stroke patients may be associated with problems at the second control level. This implies some strategies for the rehabilitation of stroke patients with motor disorders. Treatment aimed at improving arm function should be oriented toward restoring the normal sensorimotor relationships between the joints. We also found that while clinical spasticity scores were correlated with some aspects of motor performance, they provided little information about the movement deficit itself.

Movement Smoothness Changes during Stroke Recovery

“…This indicates that movement smoothness is a result of a learned, coordinative process rather than a natural consequence of the structure of the neuromuscular system. Additionally, there is evidence that the segmented nature of stroke patients' arm movements can be attributed to a deficit in interjoint coordination (Levin, 1996). Taken with our observation that smoothness increases with recovery, the conclusion that smooth movement is a result of well developed coordination seems inescapable.…”

Consequences of increased neuromotor noise for reaching movements in persons with stroke

“…The formation and calibration internal models may be impeded by damage to areas of the brain where the model is formed, and also by the increased sensory noise which would result in poorer estimations of the arm's actual behaviour (Saunder and Knill, 2004). There is some evidence that there is a reduced ability to form an appropriate internal model following stroke, including altered feedforward control of the passive intersegmental joint torques during reaching movements (Beer et al, 2000) which would result in joint in-coordination (Levin, 1996) and poorer anticipatory control of arm movements to perturbations .…”

Augmented Feedback Using Visual Cues for Movement Smoothness during Gait Performance of Individuals with Parkinson’s Disease

“…Postural control during locomotion requires the integration of multiple sensory and motor pathways so that the central nervous system can coordinate the postural and movement components of the task 16) . Previous studies have shown that nervous system problems may occur with aging, and this may lead to less smooth movement [17][18][19] . These previous studies also suggested that movement smoothness is a result of learned coordination, and increases with recovery, because the segmented nature of a stroke patient's arm movement can be attributed to a deficit in interjoint coordination 18,19) .…”

“…Previous studies have shown that nervous system problems may occur with aging, and this may lead to less smooth movement [17][18][19] . These previous studies also suggested that movement smoothness is a result of learned coordination, and increases with recovery, because the segmented nature of a stroke patient's arm movement can be attributed to a deficit in interjoint coordination 18,19) . Therefore, the results of the present study suggest that visual cues improve a deficit in interjoint coordination in the lower extremities.…”