Cerebral sources of electrical potentials related to human vocalization and mouth movement.

Self-paced voluntary movements are reflected in scalp recordings of electrical potentials. Here the cerebral sources of the electrical wave forms related to human mouth movement and vocalization were identified non-invasively. Seven healthy volunteers performed vocalization and silent puckering movements. Movement-related cortical potentials (MRCP) were recorded with 30 electrodes. Source analysis of 404 ms window of MRCP revealed eight sources for vocalization and seven sources for puckering. A left frontal source (not present in puckering) accounted for 23% of the vocalization activity. Other active brain areas were the same in the two tasks. This evidence supports the idea that the left frontal lobe is activated before vocalization but not before motor act alone.