The Effects of Cerebellar rTMS on Brain Activity

Experiment The optimal motor stimulation sites for pharyngeal and thenar cortical areas and the cerebellum will be identified and marked using single pulse TMS with a coil. Anatomical landmarks will be used to help guide neuronavigation. The vertex (top) of the head will be identified with a tape measure as will the inion (the most prominent part at the back of the skull). Studies have demonstrated that pharyngeal (throat) and thenar (thumb) cortical areas are found in front and to the side of the vertex while both halves of the cerebellum lie below and to the side of the inion. The thenar resting motor threshold over the dominant pharyngeal hemisphere is required for calculation of cerebellar rTMS intensity. Participants will then be randomly allocated to either real right sided cerebellar rTMS or sham (pretend) cerebellar rTMS on each visit. Each participant will undergo both procedures (real and sham) over the course of their involvement with the study. Real cerebellar rTMS will be delivered by holding the figure of eight coil flat against the head. It will be administered at 90% of thenar resting motor threshold at a frequency of 10 Hertz. Sham cerebellar rTMS will be delivered by holding the coil perpendicular to the scalp with only the edge of the coils making contact with the head. This technique has been used in previous studies and will ensure that no stimulation is delivered to the cerebellum. After real or sham cerebellar rTMS, participants will have functional magnetic resonance imaging (fMRI) scans of their brains. During the scan participants will be asked to swallow water through a plastic tube. This will activate their brain swallowing centres. Each participant will be asked to complete five swallowing cycles. Each cycle will involve swallowing 10 times with a one second gap between swallows. Cycles will be separated by a 10 second period of rest.