Change in Brain Blood Flow before and after Chewing Using Near-Infrared Spectroscopy

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The purpose of this experiment was to clarify the relationship between masticatory movement and brain blood flow.Forty healthy subjects (20 males and 20 females) in their twenties were asked to chew a piece of chewing gum on their habitual chewing side. The masseter muscular activity using EMG, the surface blood flow using laser bloody flow meter, and the deep blood flow of the forehead and temporal region using NIRS (Near-infrared spectroscopy) were recorded simultaneously. The change of the deep blood flow of the forehead and the temporal region during mastication were investigated and then compared between the amount of blood flow in the brain and the integral values of masseter muscular activities.Though the surface blood flow of the forehead did not change during mastication, the deep blood flow of the forehead increased during mastication and returned to its original state. It was confirmed that the device used in this experiment could detect the brain blood flow without the influence of muscular activity, and the probe of the anterior temporal region also could detect the brain blood flow.The brain blood flow increased during mastication and decreased when mastication ceased and returned to its original state. And the integral values of masseter muscular activity and the blood flow in the brain were smallest at weak period and increased in order of medium period and strong period. A significant difference was found between the periods. From, these results it was concluded that the blood flow in the brain did increase by masticatory movement and the strength of the muscular activity affected the changes of brain blood flow.