Because no detailed information exists regarding the topographic representation of swallowing musculature on the human cerebral cortex in health or disease, different functional imaging methods are used to study the cortical topography of human oral, pharyngeal and esophageal musculature in healthy individuals and in patients. The findings demonstrate that swallowing musculature is discretely and somatotopically represented on the motor and premotor cortex of both hemispheres but displays interhemispheric asymmetry, independent of handedness. Following stroke, dysphagia appeared to be associated with smaller pharyngeal representation on the intact hemisphere, which increases in size with recovery of swallowing. Lesional and electrophysiological data implicate a role for the cerebral cortex in the initiation and modulation of human swallowing, and yet its functional neuroanatomy remains undefined. We conclude that volitional swallowing recruits multiple cerebral regions, in particular sensorimotor cortex, insula, temporopolar cortex, cerebellum, and brain stem, the sensorimotor cortex displaying strong degrees of interhemispheric asymmetry and might help to explain the variable nature of swallowing disorders after stroke and other focal lesions to the cerebral cortex.
