Brain Activations of Deglutition in Normal Adult Humans -fMRI Study

Objectives: The purpose of this study was to explore the brain activation of volitional deglutition in normal adult humans using functional MRI (fMRI). Methods: Six healthy young adults (three females and three males, 27-31 yrs of age, right-handed, non-smokers) participated in this study. The Human Experimentation Committee of Kyushu University approved all experimental procedures. The participants underwent MRI in a 3T scanner, and functional EPI images and three-dimensional anatomical images were acquired. In the experiment, small volume of tasteless artificial saliva (25 mM KCl plus 2.5 mM NaHCO₃) was delivered 32 times through original intra-oral and computer-controlled extra-oral devices. The participants swallowed the artificial saliva at the timing of tone signals. Data analysis was performed using the Statistical Parametric Mapping 8 software (WTCN, London, UK). To remove the artifacts by the head movements of the participants during deglutition, the images were realigned, and then the estimated movement parameters were included as covariates in the design matrix. First, the activation of each subject was investigated and anatomically identified on her/his own brain anatomy. Second, each individual data set was entered into the group analysis (conjunction analysis) to infer the typical characteristics of the participants. Results: Multiple regions of highly significant activations were obtained with the volitional deglutition (p < 0.05 Family Wise Error corrected). Those activation foci were located in the pre- and postcentral gyri (the primary motor and somatosensory cortices, respectively), the anterior cingulated cortex (corresponding to affective/attentive reactions), the insula (sensory-motor integration), as well as in areas of the thalamus (relay station for sensory information) and the cerebellum (adaptive modulation). Conclusion: The brain activities of deglutition were represented in many of the spatially and functionally distinct cortical regions which work differently in the regulation of deglutition. (Grants in Aid of Scientific Research from the Ministry of Education, Japan 19390479)