Does the pre-frontal cortex contribute to movement-related potentials? Recordings from subdural electrodes.

The contribution of the pre-frontal cortex to movement-related potentials (MRPs) is unclear. We recorded MRPs from six subdural electrode strips placed over the frontal cortex in a 13-year-old girl being monitored prior to surgery for intractable epilepsy. MRPs were recorded prior to two types of movement: self-paced random joystick movements which involve 'what to do' and 'when to do' decision making on every trial and prior to joystick movements in a fixed forward direction triggered by a tone which does not involve any trial-by-trial decision making. Self-paced random joystick movements were associated with an increased subdural positivity starting from 1000 ms prior to onset of joystick movement at electrodes over the pre-motor cortex (BA 6) and dorsolateral and inferior pre-frontal cortex (BA 46/45/10), as evident from a magnetic resonance imaging scan. These results suggest that in addition to the pre-motor area, the pre-frontal cortex also contributes to the generation of MRPs in conditions involving decision making about the precise nature ('what to do') and timing ('when to do') of the movement. These preliminary results require replication in a larger series of patients.