Effect of mastication on regional cerebral blood flow in humans examined by positron-emission tomography with 15O-labelled water and magnetic resonance imaging

The interaction between mastication and cerebral blood flow was studied in 12 healthy volunteers (five males and seven females) aged 18–40 years. Positron-emission tomography (PET)-autoradiography was carried out after bolus injection of 1.5 GBq H215O (15O-labelled water) with a half life of 2 min. The PET images were superimposed on magnetic resonance images of each participant. The regional cerebral blood flow images were normalized by the global cerebral blood flow value, and subtraction images (those during gum-chewing minus those during resting) were created and recut at the magnetic resonance image slice positions. Gum specially designed for chewing training was used. Mastication increased regional cerebral blood flow in the primary sensorimotor areas by 25–28%, in the supplementary motor areas and insulae by 9–17%, and in the cerebellum and striatum by 8–11%. These increases demonstrate that chewing activates widespread regions of the brain.