WATANABE Kazuko Gifu University, School of Medicine, Assistant professor, 医学部, 講師 (40158621)
FUJITA Masafumi Gifu University, School of Medicine, Assistant professor, 医学部, 講師 (50021449)
NISHIYAMA Katsuhiro Kanagawa Dental College, School of Dentistry, Assistant professor, 歯学部, 講師 (20084783)
藤原 周 朝日大学, 歯学部, 助教授 (50229069)
久保 金弥 朝日大学, 歯学部, 講師 (00329492)
|Budget Amount *help
¥13,100,000 (Direct Cost : ¥13,100,000)
Fiscal Year 2003 : ¥3,200,000 (Direct Cost : ¥3,200,000)
Fiscal Year 2002 : ¥9,900,000 (Direct Cost : ¥9,900,000)
In recent years, much effort has been devoted to evaluating the interaction between chewing and blood circulation in the human brain ; as a result, age-related changes of chewing-induced brain neuronal activity have been suggested. In this study, we used functional magnetic resonance imaging (fMRI) to assess the effect of aging on brain regional activity associated with chewing in young adult ( 19-26 yrs), middle-aged (42-55 yrs), and aged (65-73 yrs) healthy humans.
Using fMRI during cycles of rhythmic gum-chewing and no chewing, we found that, 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. These findings suggest that chewing may stimulate functionally memory-related regions in the cerebra cortex.
In addition, during picture encoding, chewing caused a significantly higher increase of the BOLD signals in the hippocampus, being believed to play an indispensable brain region for memory formation, in comparison with those without chewing, implying involvement of chewing in the hippocampal network system. Furthermore, two weeks after wearing the full dentures of the aged subjects who had never worn them, higher value of the hippocampal BOLD signals were caused during picture encoding.
These results indicate that masticatory function plays a crucial role in maintaining and/or recovering learning and memory in the elderly.