Chewing-induced activation and regeneration of neuronal circuits in human brain

本研究旨在探讨咀嚼器官与大脑及海马等高级脑组织之间的串扰机制。特别是，我们集中在咀嚼刺激对老年人的记忆过程的预防作用，使用功能磁共振成像（fMRI）技术和行为的方法。在第一个实验中，使用功能磁共振成像在有节奏的口香糖咀嚼和没有咀嚼，我们研究了在年轻的成年人，中年人，老年人完整的人类咀嚼过程中的大脑区域活动的影响。在所有受试者中，咀嚼导致感觉运动皮层、小脑、丘脑、辅助运动区和额叶皮层的BOLD信号双侧增加，右侧前额叶区单侧增加。在前三个区域中，信号增加以年龄依赖的方式衰减，而在右前额叶区，则匡威。另外，我们还进行了另一项fMRI实验，通过使用包含空间认知功能的照片的任务，研究咀嚼对海马活动的影响。结果，年轻受试者的海马体被强烈激活，但咀嚼前后没有显著差异。相反，老年人的激活与年轻受试者相比相当小。而咀嚼使激活面积和fMRI信号强度增加。此外，根据回忆测试的结果，老年受试者在咀嚼后的记忆获得显着增加。此外，戴义齿后，海马活动和记忆获得增加。这些结果有力地表明，在老年人中，咀嚼导致增强和/或维持依赖于大脑皮层的认知记忆。

The goal of this project is to elucidate the crosstalk mechanism(s) between the masticatory organs and the higher brain including the cerebral and the hippocampus. Especially, we focused on the preventive effect of Chewing stimulus on memory processes in aged humans, using the functional magnetic resonance imaging (fMRI) technique and the behavioral method. In the first experiment, using fMRI during 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.Furthermore, increases in hippocampal activities and memory acquisition were recognized after denture wearing. These results strongly suggest that, in the elderly, chewing causes an enhancement and/or maintaining in hippocampus-dependent cognitive memory.