To reveal the interaction between the motor speech areas and the auditory areas during vocalization, brain activity during reading tasks was examined using Positron Emission Tomography (PET). The regional cerebral blood flow (rcBF) of six normal subjects was measured at rest, while reading everyday sentences silently, and while reading aloud. Regions of interest (ROIs) were set on the primary auditory area, the auditory association area, Broca's area, the motor area, the supplementary motor area (SMA) and the cerebellum. We subtracted rcBF data in ROIs during resting from those during each reading task, and evaluated the areas in which rcBF increased during each task. During silent reading, Broca's area, the SMA, and the cerebellum were activated bilaterally. During reading aloud, the primary auditory area, Broca's area, the motor area, the SMA, and the cerebellum were activated bilaterally, but the auditory association areas were not activated, even though the subjects heard their own voice. These results suggest that the activity of the auditory association area is suppressed when vocalizing everyday sentences. They also show a reasonable interaction between the motor speech areas and the auditory areas during vocalization.
