The bereitschaftspotential preceding stepping in patients with isolated gait ignition failure.

The cerebral activity preceding voluntary, self-paced ankle dorsiflexion movements while seated was compared with that before a stepping movement of the same foot while standing in four patients with isolated gait ignition failure. Results within the patients group were variable, but all exhibited some increase in the Bereitschaftspotential (BP) amplitude when stepping as compared with sitting, similar to that seen in normal subjects. This differs from previous results in patients with Parkinson's disease in which stepping was not accompanied by a normal increase in BP amplitude. This difference suggests that the mechanisms responsible for the start hesitation that is common to both Parkinson's disease and gait ignition failure may differ in the two conditions.