Stability of Motor Output in Aging Adults

A large number of our nation's veterans develop dysphagia due to the myriad of potential etiological sources of swallowing disorders, including stroke and head and neck cancer. The Veteran's Health Administration has recently identified dysphagia as a major clinical focus for the VA system (Sullivan & Dennis, 2006). In order to accurately assess adaptations in motor cortex, it is first necessary to have a reliable tool for measuring organizational representation in the motor cortex. Transcranial magnetic stimulation (TMS) is a desirable choice for such measurement because of the ability to identify causative relationships between an area of motor cortex stimulated and muscle response. Therefore, the specific research objectives of this proposal are:

1. To demonstrate the reproducibility of TMS mapping of the submental muscle group in healthy older adults between 60 and 80 years of age
2. To determine the neural representation of submental musculature in the motor cortex of healthy older adults between 60 and 80 years of age.

Twenty healthy adults, 10 men and 10 women, between the ages of 60 and 80 years will serve as research participants. TMS will be used to establish motor maps of the submental muscles. Subjects will undergo two testing sessions, on day 1 and day 14. The results from each session will be compared to assess excitability and representation within the motor cortex, and to assess stability and reliability of measurement.