Changes of regional cerebral blood flow measured simultaneously in the right and left hemisphere during automatic speech and humming.

Regional cerebral blood flow (rCBF) was measured simultaneously in both hemispheres during automatic speech and during humming. During automatic speech rCBF increased slightly but significantly more in the right hemisphere. No side difference was found during humming. At rest and in both test situations the rCBF was highest bifrontally. Regional analysis revealed multiple regions of significantly increased rCBF in both hemispheres during both speech and humming. Some of these regions coincided with known speech centres in the left hemisphere. Others, especially on the right, did not. It is concluded that vocal activation during both speech and humming requires a collaboration of the two hemispheres in various functional patterns.