PARKINSONISM REDUCES COORDINATION OF FINGERS, WRIST, AND ARM IN FINE MOTOR CONTROL

This experiment investigates movement coordination in Parkinson's dise ase (PD) subjects. Seventeen PD patients and 12 elderly control subjec ts performed several handwriting-like tasks on a digitizing writing ta blet resting on top of a table in front of the subject. The writing pa tterns, in increasing order of coordination complexity, were repetitiv e back-and-forth movements in various orientations, circles and loops in clockwise and counterclockwise directions, and a complex writing pa ttern. The patterns were analyzed in terms of jerk normalized for dura tion and size per stroke. In the PD subjects, back-and-forth strokes, involving coordination of fingers and wrist, showed larger normalized jerk than strokes performed using either the wrist or the fingers alon e. In the PD patients, wrist flexion (plus radial deviation) showed gr eater normalized jerk in comparison to wrist extension (plus ulnar dev iation). The elderly control subjects showed no such effects as a func tion of coordination complexity. For both PD and elderly control subje cts, looping patterns consisting of circles with a left-to-right forea rm movement, did not show a systematic increase of normalized jerk. Th e same handwriting patterns were then simulated using a biologically i nspired neural network model of the basal ganglia thalamocortical rela tions for a control and a mild PD subject. The network simulation was consistent with the observed experimental results, providing additiona l support that a reduced capability to coordinate wrist and finger mov ements may be caused by suboptimal functioning of the basal ganglia in PD. The results suggest that in PD patients fine motor control proble ms may be caused by a reduced capability to coordinate the fingers and wrist and by reduced control of wrist flexion. (C) 1997 Academic Pres s.