Motor dysfunctions in Parkinson's disease and premotor lesions

A characteristic disturbance of hand function in Parkinson's disease lies in the performance of rapid automatized movements. Patients have difficulty in producing serial hand movements faster than 2 Hz. The only possibility to perform rapid alternating movements is to synchronize them with their tremor frequency. This mechanism underlies the so-called 'hastening' phenomenon and leads to a disturbance of skills like handwriting or typing, which are usually performed at higher frequencies. The temporal disorder in patients with lesions of premotor cortex is characterized by the difficulty in organizing higher order temporal sequences in complex motor acts.