Brain Function for Enjoying Meal-Study by Using Positron CT

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At first, the study was designed to quantify the local and overall activity of masticatory muscles and the brain during lateral excursion of the mandible using FDG-PET. Eleven healthy young male volunteers who had normal masticatory function participated in the study. Each subject received an injection of 39.2 +/-5.2 MBq of ^<18>F-FDG into the cubital vein. Just after the injection, each subject was asked to start left lateral excursion of the mandible at 1.0 Hz and then continued for 30 min. As results, the mean SURs of contralateral lateral pterygoid and medial pterygoid muscles were significantly higher than those of the bilateral masseter muscles. There was large variation in the FDG accumulation of the masticatory muscles during function among subjects and muscle activities of each subject showed individual manner. However it was difficult to characterize the brain activities during mandibular function by PET images.Therefore functional magnetic resonance imaging (fMRI) was also applied to analyze the brain function during gum chewing. In the MR Scanner (Siemens Magnetom Vision Plus, 1.5T), subjects (three males) wearing earplugs in a supine position were instructed to perform the following task : chewing gum with no taste and orange taste as taste stimuli and watching the projected images of the cutting surface of an orange and an orange colored mosaic as visual stimuli. Combining these stimuli, MR imaging under four conditions were carried out. As results, much activities in the parietal and temporal lobes were observed when both of taste and visual stimuli were applied than when both were not. On the other hand, the image of an orange and the occluded image as visual stimuli had no effect on the difference between the brain activities with and without taste stimuli.