| Mastication is one of the most important fundamental oral functions. A highly refined neurologic control system regulates and coordinates the activities of the entire masticatory system. At the same time, mastication has great effects on brain function as well as general health, such as brain flood flow, memory and development. Although neurologic control of mastication was extensively studied previously, the underlying mechanism is far from completely clear now, much less the metabolism in the activated brain areas related to mastication. With the rapid development of functional imaging techniques, including functional magnetic resonance imaging and magnetic resonance spectroscopy, brain science was pushed forward greatly in recent 10 years. At present, these techniques have provided new insights into the functional neuroanatomv of sensory, motor, cognitive processes. Application of these techniques to mastication has just set out domestic and abroad. The results differes from studies. The present studies observed the effects of unilateral mastication on brain function with functional magnetic resonance imaging and detected the metabolic changes related to mastication inactivated brain area with magnetic resonance spectroscopy. This thesis consists of the following two parts:1. A study on metabolic changes in cortices caused by mastication with magnetic resonance spectroscopyObjective: The aim of this study was to observe the metabolic changes caused by bilateral mastication in functional areas associated with mastication in frontal lobe, and to explore the feasibility of using magnetic resonance spectroscopy to study the relationship between mastication and brain function. The second objective was to establish the basis for further study of relationship between mastication and brain function in patients with oral diseases. Materials and methods: The metabolic changes were detected with magnetic resonance spectroscopy in 10 healthy volunteers. The changes under the rest and motor conditions were compared statistically. Results: The concentration of lactate increased significantly during mastication, while there were no obvious changes in other metabolites. Conclusions: Mastication can lead to the increase of lactate in cortical masticatory area. The increment of lactate, which may be the product of glycolysis during activation of neurons, suggests that energy demand of neural activity may be met by anaerobic glycolysis. Magnetic resonance spectroscopy can be applied to the research field relevant to the relationship between mastication and brain function with reliability.2. A study on unilateral mastication with functional magnetic resonance imagingObjective: The aim of this study was to observe the neuronal activities related to unilateral mastication in cortex and to explore effects of mastication on brain function. Materials and methods: The neuronal activities related to unilateral mastication were detected with functional magnetic resonance imaging in 10healthy volunteers. Results: Localization of activation was significantly different between left-sided and right-sided mastication in group analysis as well as in individual analysis. The difference between left-sided and right-sided mastication may come from individual difference. Brain activation was comprehensive during mastication. Conclusions: 1. It is suggested contralateral hemispheric dominance for the control of unilateral mastication. 2. There is significant difference in the control of left-sided mastication and right-sided mastication, which may be the result of inter-subjects difference. 3. The functional areas related to mastication and speech are closely connected, which indicates close relationship between mastication and speech. The roles of activated brain regions in mastication still remain to be elucidated. |
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