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This Article Full Text Full Text (PDF) All Versions of this Article: 585/2/525    most recent jphysiol.2007.144592v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Mistry, S. Articles by Hamdy, S. Search for Related Content PubMed PubMed Citation Articles by Mistry, S. Articles by Hamdy, S. Related Collections Neuroscience

¹ University of Manchester, Department of Gastrointestinal Sciences, Hope Hospital, Salford M6 8HD, UK
² Department of Physiology, Rouen University Hospital, 1 rue de Germont, 76031 Rouen and UPRES EA 3830 IFRMP 23, GRHV Research Group, Rouen University, Rouen, France
³ Institute of Neurology, Sobell Department of Motor Neuroscience and Movement Disorders, Queen Square, London WC1N 3BG, UK

Inhibitory patterns of repetitive transcranial magnetic stimulation (rTMS) were applied to pharyngeal motor cortex in order to establish its role in modulating swallowing activity and provide evidence for functionally relevant hemispheric asymmetry. Healthy volunteers underwent single pulse TMS before and for 60 min after differing intensities of 1 Hz rTMS (n = 9, 6 male, 3 female, mean age 34 ± 3 years) or theta burst stimulation (TBS) (n = 9, 6 male, 3 female, mean age 37 ± 4 years). Electromyographic responses recorded from pharynx and hand were used as a measure of cortico-motor pathway excitability. Swallowing behaviour was then examined with a reaction time protocol, before and for up to 60 min after the most effective inhibitory protocol (1 Hz) applied to each hemisphere. Interventions were conducted on separate days and compared to sham using ANOVA. Only high intensity 1 Hz rTMS consistently suppressed pharyngeal motor cortex immediately and for up to 45 min (–34 ± 7%, P 0.001). Adjacent hand and contralateral pharyngeal motor cortex showed no change in response (–15 ± 12%, P = 0.14 and 15 ± 12%, P = 0.45, respectively). When used to unilaterally disrupt each hemisphere, rTMS to pharyngeal motor cortex with the stronger responses altered normal (–12 ± 3%, P 0.001) and fast (–9 ± 4%, P 0.009) swallow times, not seen following rTMS to the contralateral cortex or after sham. Thus, suppression of pharyngeal motor cortex to rTMS is intensity and frequency dependent, which when applied to each hemisphere reveals functionally relevant asymmetry in the motor control of human swallowing.

(Received 5 September 2007; accepted after revision 10 October 2007; first published online 11 October 2007)
Corresponding author S. Hamdy: University of Manchester, Department of Gastrointestinal Science (Clinical Sciences Building), Hope Hospital, Salford, Manchester M6 8HD, UK. Email: shaheen.hamdy{at}manchester.ac.uk