Functional MRI study of cerebral cortical activation during volitional swallowing

Objectives: To investigate the somatotopic distribution and lateralization of motor and sensory cortical activity during swallowing in healthy adult human subjects using functional MR imaging. Methods: Nine healthy right-handed adult volunteers (6 men, 3 women; ages 22-38) were examined. Their cortical activities were evoked by having them swallow, five times, a small bolus of water (3 ml) supplied through a plastic catheter. As a positive control, the subjects performed five repetitions of right-handed grasping tasks. Blood oxygenation level-dependent images were obtained using a 1.5 Tesla MR system (Magnetom Vision, Siemens Germany; TR/TE=0.96/0.66, FA=90°). Tl weighted anatomical images were obtained for the same slices in each subject. Results: Cerebral activity was observed most notably in the primary motor cortex and primary somatosensory cortex, followed by the premotor cortex, anterior cingulate cortex, frontal operculum, and insula. The hand-grasping task activated relatively superior parts of the primary motor and somatosensory cortices. The swallowing task, on the other hand, activated the inferior parts of the pre- and postcentral gyri. The hand-grasping activation of motor and sensory cortices was localized absolutely on the contralateral side, whereas swallowing activated the motor cortex either bilaterally or unilaterally. Swallowing activated the sensory cortex almost always bilaterally. Conclusions: This study suggested that fMRI could be used to identify the specific areas of cortical activation caused by various tasks, and to differentiate the locations of cortical activation between tasks.