Preventive effects of masticatory stimulus on senile dementia : a fMRI study

本研究旨在探讨咀嚼器官与大脑皮层（包括海马）之间的串扰机制。特别是，我们集中在咬合或咀嚼刺激对老年人的记忆过程的预防作用，通过功能磁共振成像（fMRI）和行为科学。在第一个实验中，使用功能磁共振成像在周期的节奏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。无论是咀嚼训练和沟通在用餐或义齿佩戴者的情况下，记忆获得的组合效果也显着。从上述结果，我们强烈建议，在老年人，咬合或咀嚼刺激引起的增强，在海马依赖的记忆获得。

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.