The Bereitschaftspotential preceding simple foot movement and initiation of gait in Parkinson's disease.

We compared the Bereitschaftspotential preceding a simple foot movement while sitting and a stepping movement while standing in a group of normal subjects and seven patients with mild to moderate Parkinson's disease (PD) while off medication. None had major difficulties stepping to initiate gait. Electromyographic signals from tibialis anterior triggered the averaging of electroencephalographic signals from the scalp. Bereitschaftspotential preceding a standing stepping movement were larger than those before a foot movement while sitting in normal subjects, but no difference was observed in patients with PD. The absence of an increase in the Bereitschaftspotential when stepping in PD may reflect an impairment of the preparation and assembly of the complex sequences of movement necessary to initiate walking, even in the early stages of the illness.