Abstract
A new method to measure movement-related cortical potentials (MRCP) using an external stimulation guidance was developed for easy application to patients with movement disorder. Normal findings for MRCPs associated with the gait were determined in 30 normal subjects aged between 20 and 79 years. There were at least 5 subjects in each decade of the age range. The external guidance was a hand on a clock which moved from 9 o'clock to 12 o'clock during 5 sec. Subjects standing 1.5 m in front of the clock took 2 steps when the hand pointed to 12 o'clock (trigger). EEGs before and after the starting point of the gait were recorded in each subject. EEGs were also recorded during non-gait movement when the hand on the clock pointed to 12 o'clock. The mean difference waveforms were obtained by subtracting the mean waveform for non-gait from that for gait MRCP. The gait MRCP showed a slow potential shift in all subjects which corresponded to the Bereitschaftspotential (BP). The BP started from 1,082 ± 320 msec before the trigger with symmetric distribution. The mean amplitude of the BP at the trigger was 7.8 ± 3.6 μ V. and tended to increase with age. The BP became steeper from 501 ± 175 msec preceding gait in 21 subjects which corresponded with negative slope (NS'). The frequency of NS' increased with age. NS' is known to become clear and the amplitude increases with complex tasks compared with simple tasks, so the present results suggest that gait may transform from simple to complex with age.
