Cortical potentials associated with voluntary foot movement in man

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In order to clarify the functional significance of some components of the movement-related cortical potential, averaged cortical potentials associated with brisk voluntary, self-paced foot dorsiflexion and middle finger extension were compared in 8 healthy subjects. Simultaneous recording and averaging, by an opisthochronic averaging program, of 14 channel EEGs, EOG and EMG revealed a different topographical distribution for the various components in the two kinds of movement. A negative slope occurring within 400 to 500 msec of the EMG peak (NS') was maximal over the midline precentral region and symmetrically distributed in foot movement, but was localized to the contralateral precentral region in finger movement. In contrast, an earlier negative shift (Bereitschaftspotential, BP) showed a similar distribution for both foot and finger movements. It is concluded that the NS' is specifically related to the movement, whereas the BP is related to a non-specific preparation of the cerebral cortex for voluntary movement. A small negative component occurring in close association with the EMG peak, a post-motion frontal negativity, a post-motion positivity over the parietal and precentral region and a large, widespread post-motion positivity also showed a midline pre-dominance with symmetric distribution in foot movement versus a contralateral pre-dominance in finger movement. The post-motion frontal negativity for foot movement ( N + 110 ) occurred approximately 50 msec later than that for finger movement ( N + 50 ) with respect to the EMG peak, suggesting that this component represents the kinaesthetic feedback from muscle afferents.