Discontinuities in slow finger movements in patients with Parkinson's disease.

Slow finger movements in healthy humans are characterized by discontinuous rhythmic changes in a low frequency band about 8 Hz. These pulsatile changes in velocity are thought to present the central output of an oscillatory cerebello-thalamo-cortical network in the same frequency. Hypothesizing that patients with Parkinson's disease (PD) in the dopaminergic OFF- and ON-condition show changes in the characteristics of discontinuities compared to healthy humans, we used a 3D-ultrasound device to measure slow finger movements of 16 patients with PD and 12 age-matched controls. We provide evidence that slow finger movements of patients with PD are characterized by discontinuities in acceleration, which are significantly slower in the OFF- but not in the ON-condition compared to healthy controls. Correlation analysis between clinical motor improvement after dopaminergic medication and changes of peak frequencies and peak power of discontinuities was not significant. We conclude that the oscillatory brain network of slow finger movements is affected in PD, presenting in a lower frequency in the OFF-condition. We suggest that one factor of the modulation of this network is a dopaminergic stimulation.