Cerebral cortical representation of automatic and volitional swallowing inhumans

Although the cerebral cortex has been implicated in the control of swallowi ng, the functional organization of the human cortical swallowing representa tion has not been fully documented. Therefore, the present study determined the cortical representation of swallowing in fourteen healthy right-handed female subjects using single-event-related functional magnetic resonance i maging (fMRI). Subjects were scanned during three swallowing activation tas ks: a naive saliva swallow, a voluntary saliva swallow, and a water bolus s wallow. Swallow-related laryngeal movement was recorded simultaneously from the output of a bellows positioned over the thyroid cartilage. Statistical maps were generated by computing the difference between the magnitude of t he voxel time course during 1) a single swallowing trial and 2) the corresp onding control period. Automatic and volitional swallowing produced activat ion within several common cortical regions, the most prominent and consiste nt being located within the lateral precentral gyrus, lateral postcentral g yrus, and right insula. Activation foci within the superior temporal gyrus, middle and inferior frontal gyri, and frontal operculum also were identifi ed for all swallowing tasks. In contrast, activation of the caudal anterior cingulate cortex was significantly more likely in association with the vol untary saliva swallow and water bolus swallow than the naive swallow. These findings support the view that, in addition to known brain stem areas, hum an swallowing is represented within a number of spatially and functionally distinct cortical loci which may participate differentially in the regulati on of swallowing. Activation of the insula was significantly lateralized to the right hemisphere for the voluntary saliva swallow, suggesting a functi onal hemispheric dominance of the insula for the processing of swallowing.