Cortical processing of unplanned movement sequences involving hands and feet: evidence from event-related potentials.

The neural processes underlying an unplanned shift in movement control across limb systems were studied by recording event-related potentials (ERPs) as participants made a left or right hand movement followed by a left or right foot movement or vice versa. ERPs associated with both first and second movements replicated a recent finding that Cz is more positive before hand than foot responses. Lateralized readiness potentials (LRPs) associated with the first movement replicated patterns observed previously with single movements, but LRPs leading up to the second movement depended strongly on the side of the first movement, possibly because of residual lateralization from it. Overall, the results suggest that the motor processes associated with limb system selection can be fully reset prior to a switch between hand and foot movements, but the processes associated with side selection may not be.