Delineation of voluntary movement in Parkinson's disease with the manual control system

An assessment of the dynamic characteristics of voluntary movement in 20 patients with Parkinson's disease and 20 normal subjects was performed by the manual control system. The following eight parameters were estimated and mapped on the plane with eight axes: gain constant between the input and the output, cut frequency for evaluation of the frequency response of human operator, dead time, square error, correlation coefficient, and three different points of coherency for the measurement of the linearity of human operation. In Parkinson's disease, we found a low gain constant of 8.34 +/- 9.64 dB (mean +/- S.D.) (26.5 +/- 2.12 in controls), a narrow cut frequency of 1.08 +/- 0.91 radians/sec (5.65 +2- 1.25), a long dead time of 0.79 +/- 0.27 sec (0.19 +/- 0.05), a large square error, a low correlation coefficient, and low points of coherency. Among the eight parameters, the gain constant and the dead time proved to be the most useful for quantitative assessment of motor disability for this disorder. Our method promises to be valuable to confirm the effects of drug therapy and the progression of the disease.