| Co-Investigator(Kenkyū-buntansha) |
SATO Sadao Kanagawa Dental College, Dentistry, Professor, 歯学部, 教授 (00084799)
UEMATSU Hiroshi Tokyo Medical and Dental University, Professor, 大学院・医歯学総合研究科, 教授 (80100957)
KATO Norihiro Gifu University Hospital, Faculty of Medicine, Associate professor, 医学部付属病院, 助教授 (40224521)
KANEMATSU Masayuki Gifu University Hospital, Faculty of Medicine, Associate professor, 医学部付属病院, 助教授 (40252134)
WATANABE Kazuko Gifu University, Graduated School of Medicine, Associate professor, 大学院・医学系研究科, 助教授 (40158621)
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| Research Abstract |
The goal of this project is to elucidate the crosstalk mechanism(s) between the masticatory organs and the cerebral cortex including the hippocampus. Especially, we focused on the preventive effects of occlusal or masticatory stimulus on memory processes in aged humans, by the functional magnetic resonance imaging (fMRI) and behavioral science. In the first experiment, using fMRI during cycles of rhythmic gum-chewing and no chewing, we examined the effect of aging on brain regional activity during chewing in young adult, middle-aged, and aged intact humans. In all subjects, chewing resulted in a bilateral increase in the BOLD signals in the sensorimotor cortex, cerebellum, thalamus, supplementary motor area, and insula, and a unilateral increase in the right prefrontal area. In the first three regions, the signal increases were attenuated in an age-dependent manner, whereas, in the right prefrontal area, the converse was seen. The remaining two regions showed no significant differences with ages.
We did another fMRI experiment, in which we examined the effect of chewing on the hippocampal activities, by employing a task using photographs containing spatial cognitive function. As a result, the hippocampus in young subjects was strongly activated, but no significant difference was seen between before and after chewing. In contrast, activation in the elderly was quite small in comparison with the young subjects. However, the activation area and the intensity of fMRI signals increased by chewing. Furthermore, according to the results from the recall test, aged subjects showed a significant increase in memory acquisition after chewing. Either combined effect of chewing training and communication during meals or the case of the denture wearers on memory acquisition was also significant. From the above results, we strongly suggest that, in the elderly, occlusal or masticatory stimulus causes an enhancement in hippocampus-dependent memory acquisition.
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