Role of the Anterior Cingulate Cortex in Volitional Swallowing

Objectives: It is known that the anterior cingulate cortex (ACC) is activated in volitional swallowing. Here, we tested the hypothesis that visual/somatosensory inputs given prior to volitional swallowing modulate the ACC activity using event-related functional magnetic resonance imaging (fMRI). Methods: Ten healthy volunteers participated in this study. Visual images, i.e., photographs of food (DRINK) or general items (GENERAL) that would induce or not induce a desire to drink, were used as the visual input. Placing either 2 ml of water (WATER) or no water (DRY) into the mouth was considered as somatosensory inputs. Brain activity was measured using a 1.5T MR system. First, functional images were obtained under four conditions with combinations of both visual/somatosensory inputs (DRINK/WATER, GENERAL/WATER, DRINK/DRY, GENERAL/DRY), which were randomly repeated 6 times. Results: The maximum percent changes in the MR signal in the ACC were significantly (p<0.01) greater in GENERAL than in DRINK in both the WATER and DRY conditions. Next, functional images were obtained with or without somatosensory inputs. The maximum percent changes in the MR signal were significantly (p<0.01) greater in WATER than in DRY condition. The local maxima of activation in the ACC with somatosensory inputs were rostrally localized, whereas those with both visual/somatosensory inputs were caudally localized. Conclusion: These suggest that the ACC plays an important role as an interface between volitional efforts and polymodal inputs in volitional swallowing. Supported by Grants-in-Aid (14370691/16659569).