Identification of Swallowing-related Cortical Areas in Humans Using fMRI

Objectives: It has been known that the cerebral cortex plays an important role to control swallowing movement in humans. Motor and sensory cortices are thought to be dominantly involved in swallowing movement. However, the detailed cortical mechanisms underlying swallowing movement in humans still remain unclear. To elucidate the involvement of cerebral cortex in swallowing movement, we examined activity of cortical areas during the orofacial movement tasks including swallowing using fMRI. Methods: Eight right handed healthy volunteers were participated in the present study (4 males, 4 females, age range 27-41 years, mean 33.6 ± 5.5 years). Cortical areas activated by volitional saliva, water swallowing, jaw, tongue, and hand movement were analyzed using fMRI. In the water swallowing task, a bolus of water was given to subjects with a silicon tube. Results: The primary motor cortex (MI), primary sensory cortex (SI) and cerebellum were activated during saliva or water swallowing, jaw and tongue movement. The insula, right middle frontal gyrus, cingulate gyrus and supplementary motor cortex were activated during saliva, water, swallowing, and tongue movement. Basal ganglia and left middle frontal gyrus were also activated during saliva swallowing and tongue movement, and during water swallowing, respectively. We also observed that the activation of MI and SI was significantly stronger during saliva swallowing compared with water swallowing. Conclusion: These findings suggest that several cortical regions relating sensory-motor functions are significantly involved in swallowing movement in humans.

Supported by Research Grants from Sato and Uemura Funds from Nihon University School of Dentistry, and a grant from the Dental Research Center, Nihon University School of Dentistry; Nihon University multidisciplinary research grant for KI and Japan-Canada Joint Health Research Program(#07033211-000165). Academic Frontier Project for Private Universities: "Brain Mechanisms for Cognition, Memory and Behavior" at Nihon University: a matching fund subsidy from MEXT.