Bereitschaftspotential preceding speech after holding breath

Cerebral potentials prior to speaking were recorded in 36 healthy righthanded subjects. Subjects began holding breath at irregular intervals prior to the voluntary onset of speech. This was done in order to avoid respiration-related potential shifts. The Bereitschaftspotential (BP) or readiness potential started already 2 s prior to the onset of speaking and was present over either hemisphere. During the last 100 to 200 ms of preparation period, the BP became significantly lateralized towards the left hemisphere. The close temporal relation to speech onset characterized this hemispheric lateralization to be an indicator of the final motor mechanisms for speech. Still, the BP was a bilateral phenomenon, i.e. it was also present over the right hemisphere, indicating involvement of the non-dominant hemisphere as well. The data are compatible with the view of an early bihemispheric motor preparation for speech followed by a late left hemisphere preponderance as the final common pathway.