FULL PAPER http://www.ncbi.nlm.nih.gov/pmc/arti...3/?tool=pubmed

Neuropsychologia. 2009 October; 47(12): 2504–2514.

Biased Wrist and Finger Coordination in Parkinsonian Patients during Performance of Graphical Tasks

Natalia Dounskaia,1 Arend W. A. Van Gemmert,1,2 Berta C Leis,1 and George E Stelmach1
1 Department of Kinesiology, Arizona State University, Tempe, AZ 85287
2 Now at Department of Kinesiology, Louisiana State University, Baton Rouge, LA 70803
Address for correspondence: Natalia Dounskaia, Motor Control and Biomechanics Lab, Arizona State University, P.O. Box 870404, Tempe, AZ 85287-0404, fax: (480) 965-8108, phone: (480) 727-7188, e-mail: natalia.dounskaia@asu.edu


Handwriting impairments in Parkinson’s disease (PD) have been associated with micrographia, i.e. diminished letter size. However, dyscoordination of the wrist and fingers may also contribute to handwriting deterioration in PD. To investigate this hypothesis, right-handed PD patients and controls were tested in performance of three types of cyclic wrist and finger movements: drawing of two lines and a circle. The line drawing was performed with either simultaneous flexion and extension of the wrist and fingers (equivalent pattern resulting in a right-tilted line) or with wrist flexion/extension accompanied with finger extension/flexion (nonequivalent pattern resulting in a left-tilted line). Circle drawing required a specific phase difference between wrist and finger motions. Movements were performed with an inkless pen on a digitizer-tablet at two frequency levels. Consistent deformations of the circle into right-tilted ovals and lower variability in equivalent compared with nonequivalent lines revealed preference to produce right-tilted shapes. This preference became more apparent with increased movement speed and it was amplified in PD patients. Analysis revealed that the circle deformation emerged mainly due to reduction in relative phase, while wrist and finger amplitudes remained unchanged. The results suggest that PD causes deficit characterized by strong tendency to produce certain coordination patterns between wrist and finger motions. This deficit may significantly contribute to handwriting impairments in PD by reducing the dexterity in the production of the variety of shapes of the cursive letters. Furthermore, the deficiency revealed in wrist and finger coordination may represent a more general deficit affecting control of various multi-joint movements in PD.