| Abstract No.: | A-D1149 |
| Country: | Canada |
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| Title: | CORTICAL REPRESENTATION OF LOWER FACIAL AND MASTICATORY MUSCLES MAPPED BY TRANSCRANIAL MAGNETIC STIMULATION |
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| Authors/Affiliations: | 1 Giannina Descalzi*; 1 Carolyn Gunraj; 1 Robert Chen;
1 Division of Neurology, Toronto Western Research Institute, University of Toronto, ON, Canada
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| Content: | Transcranial magnetic stimulation (TMS) has increasingly been used as a non-invasive tool to study motor function in humans.
Objectives: To determine the location and extent of the cortical representations for lower facial muscles innervated by the 7th nerve and the Masseter muscle innervated by the 5th nerve.
Methods: Here we use TMS to map the cortical representation of a lower facial muscle and the Masseter muscle in healthy controls. Motor evoked potentials (MEPs) were recorded from the Masseter and Triangularis muscles and the size, shape, and center of gravity of the cortical representation for each muscle was calculated. A figure of eight coil was used to apply cortical stimulation across 49 points on a 7cm x 7cm grid for each muscle during activity (20% of maximum voluntary contraction). Results: The Triangularis muscle is represented significantly more lateral than the Masseter muscle (p.<.05, mean distance 1.17cm). The Masseter muscle showed significant inhibition even at ISI of 10ms, whereas the Triangularis muscle did not show significant SICI at ISI of 2ms, but showed ICF with ISI of 10ms.
Conclusion: Although the cortical representations of the Masseter and Triangularis muscles overlap, the Triangularis is represented in a more lateral location than the Masseter muscle in the human motor cortex. The pattern of SICI and ICF were different for the Masseter and Triangularis muscles. These differences may be related to the different functions of masticatory and facial muscles. |
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