| Abstract: | The cerebral potentials associated with visually triggered movements of the right index finger were studied in 5 normal subjects using multichannel scalp recordings and separate stimulus and movement-locked averaging. The visually locked wave forms showed enhanced components of the passive visual evoked potential (P1-N1) with a more widespread distribution than the VEP. The amplitude of the P1-N1 complex was influenced by the reaction time but its timing was independent of the timing of the movement. In a 'move'/'no move' choice paradigm, the positive components following the P1-N1 complex were attenuated with movement and subtraction of the 'move' and 'no move' wave forms showed a movement-related negativity building up over the contralateral parietal and central regions. With movement-locked averaging, a pre-motor negativity (PMN) of comparable topography and timing to the readiness potential was found when the timing of the cuing stimulus was regular. With randomly timed stimuli, the PMN still developed but then plateaued prior to movement. It is suggested that in this situation the PMN is related to an increasing level of arousal, anticipation and preparedness to move which is then maintained pending the arrival of the stimulus and the final motor command. |
