Abstract
Readiness potential (RP) was recorded from 10 healthy right-handed subjects to investigate the effect of purposiveness of movement on RP. Subjects participated in two experimental conditions, non-purposive movement (NPM) and purposive movement (PM) in that order. Each condition was comprised of two sessions (80 trials/session). Under NPM condition subjects were instructed to pull a lever voluntarily with the right index finger. On the other hand, under PM condition subjects were instructed to pull the lever aiming at correct response force, the range of which was set on the basis of the mean voluntary force level in NPM condition. Each lever pulling movement was followed by an auditory and a visual feedback, both of which provided subjects with KR about the correctness of response force. EEG, EOG, and mechanograms were recorded and stored for off-line averaging. Both the force and the speed of movement were not changed among sessions. As regards RP, NS' (negative slope) component of RP was not clearly observed under NPM condition. However, under PM condition the waveform of RP was found to be divided into two components, BP (Bereitschaftspotential) and NS'. Though the changes in BP amplitude were not observed between two conditions, NS' amplitude was significantly larger during purposive than during non-purposive movement. Since the physical factors related movement were not changed, the results suggested that psychological factors associated with the purposiveness of movement were reflected in enhancement of NS' component.
