Cerebral Cortical Representation of Automatic and Volitional Swallowing in Humans

TLDR

The cerebral cortex is implicated in swallowing control, but its functional organization in humans remains incompletely mapped. The study aimed to map the cortical representation of swallowing in fourteen healthy right‑handed females using event‑related fMRI. Participants performed naive, voluntary, and water bolus swallows while fMRI and bellows‑recorded laryngeal motion were collected, and voxel‑wise activation maps were generated by contrasting swallow trials with control periods. Swallowing activates a network of cortical regions—including lateral precentral, postcentral, and right insula—as well as superior temporal, frontal, and opercular areas, with caudal anterior cingulate activity higher during voluntary and water swallows and right‑hemisphere dominance of the insula, supporting distinct cortical loci in swallowing regulation.

Abstract

Although the cerebral cortex has been implicated in the control of swallowing, the functional organization of the human cortical swallowing representation 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 imaging (fMRI). Subjects were scanned during three swallowing activation tasks: a naı̈ve saliva swallow, a voluntary saliva swallow, and a water bolus swallow. 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 the voxel time course during 1) a single swallowing trial and 2) the corresponding control period. Automatic and volitional swallowing produced activation within several common cortical regions, the most prominent and consistent being located within the lateral precentral gyrus, lateral postcentral gyrus, and right insula. Activation foci within the superior temporal gyrus, middle and inferior frontal gyri, and frontal operculum also were identified for all swallowing tasks. In contrast, activation of the caudal anterior cingulate cortex was significantly more likely in association with the voluntary saliva swallow and water bolus swallow than the naı̈ve swallow. These findings support the view that, in addition to known brain stem areas, human swallowing is represented within a number of spatially and functionally distinct cortical loci which may participate differentially in the regulation of swallowing. Activation of the insula was significantly lateralized to the right hemisphere for the voluntary saliva swallow, suggesting a functional hemispheric dominance of the insula for the processing of swallowing.