Stability of Motor Output in Aging Adults

Completed

Brief Summary: The goal of this project is to examine the area of the brain that controls muscle movement for a group of muscles important for swallowing, and to see how that area changes over 2 weeks of time.

Detailed Description: 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.

Recruitment & Eligibility

Inclusion Criteria

Exclusion Criteria

Primary Outcome Measures

Name	Time	Method
Mean Motor Evoked Potential Amplitude for Submental Cortical Representation	2 weeks	Cortical sites are stimulated sequentially from the SOLMT in the anterior direction. At each site, 5 pulses of 110% of the MEP threshold obtained at the SOLMT are delivered and recorded. If a site produces no MEP in 3/5 pulses it is considered non-submental. This process is continued until the entire submental representation is surrounded by non-submental responsive sites. The number of sites is used to calculate the area of submental representation. The mean sEMG amplitudes of the submental muscles for each of these sites is then calculated for the mean MEP measure.

Secondary Outcome Measures

Name	Time	Method
Motor Map Center of Gravity	2 weeks	Position on the TMS motor map with highest amplitude response to stimulation in the muscles of interest (submental muscles).
Area of Submental Representation	2 weeks	Cortical sites are stimulated sequentially from the SOLMT in the anterior direction. At each site, 5 pulses of 110% of the MEP threshold obtained at the SOLMT are delivered and recorded. If a site produces no MEP in 3/5 pulses it is considered non-submental. This process is continued until the entire submental representation is surrounded by non-submental responsive sites. The number of sites is used to calculate the area of submental representation.