The cortical potential related to sensory feedback from voluntary movements shows somatotopic organization of the supplementary motor area.

In topographic EEG mapping, the peak negativity of movement-related cortical potentials (MRCPs) occurs after the onset of movement and appears anterior to motor cortex, over the region of the supplementary motor area (SMA). This peak, referred to as the frontal peak of the motor potential (fpMP), may well be related to sensory feedback from the movement. The somatotopic organization of the SMA is such that the upper extremity is anterior to the lower extremity. We mapped the MRCPs close to the onset of EMG activity relating to finger and toe movements. The fpMP of finger movements mapped more anteriorly than that of toe movements. These maps offer additional evidence that fpMP originates in the SMA.