The functional neuroanatomy of voluntary swallowing

Swallowing is a complex physiological process involving voluntary and refle xive motor activity, sensorimotor integration, salivation, and visceral reg ulation. Despite the numerous processes required for normal deglutition, tr aditional models of the central control of swallowing only emphasize the in volvement of the brainstem and the inferior precentral gyrus (IPCG). Howeve r a number of neurological disorders involving other brain regions also cau se dysphagia. To determine the brain regions participating in voluntary swa llowing, we assayed regional cerebral blood flow (rCBF) with positron emiss ion tomography (PET) while healthy human subjects swallowed, performed late ral tongue movements, or rested with their eyes closed. Voluntary swallowin g produced strong rCBF increases within the IPCG bilaterally, the right ant erior insula/claustrum, and the left cerebellum. The maxima in these region s differed from those induced by lateral tongue movements. Swallowing also produced rCBF increases in the putamen, thalamus, and several additional co rtical areas, but these foci were not as clearly distinguishable from activ ity arising during tongue movements. These findings indicate that swallowin g involves the recruitment of a large-scale distributed neural network that includes the anterior insula and cerebellum. The distributed nature of thi s network helps to explain why so many neurological conditions produce dysp hagia.