Kok, J. (Jelmer) (2017) Dual-contraction task performance and age-related changes in inhibition. thesis, Medicine.
Full text available on request.Abstract
Usually, motor tasks performed with the right hand are controlled by motor areas in the left, contralateral hemisphere. However, older adults show also activation of the right, ipsilateral hemisphere. It is unknown whether this activation is a compensation mechanism for age-related cortical changes or a mere effect of decreased inhibition in elderly subjects. In order to elucidate the functionality of the ipsilateral activation, we measured the task performance during single-contractions and symmetrical and asymmetrical dual-contractions with both hands or the right hand and ipsilateral foot in young (mean 23 years, n=15) and older (mean 67 years, n=14) subjects. When the ipsilateral activation is functional, a hand-hand task is expected to be performed worse than an ipsilateral hand-foot task, because the motor cortex of one hemisphere would then be challenged by both the coordination of the contralateral hand and the ipsilateral compensation for age effects. During the performance of the tasks, we stimulated the primary motor cortex using transcranial magnetic stimulation in order to evoke motor evoked potentials (MEPs), short-interval intracortical inhibition (SICI), subthreshold EMG suppression and ipsilateral silent periods (iSPs) in the right first dorsal interosseous muscle as measures of cortical inhibition. Dual-contraction, but not single-contraction task performance was declined more than 45% in older adults compared to young adults. During single-contractions, no age differences in MEP size and SICI were found, but more than 55% increased facilitation was observed during stronger ipsilateral single-contractions. During dual-contractions, the MEP size decreased ~10% independent of age compared to a single-contraction; older adults showed ~40% more intrahemispheric and ~40% less interhemispheric inhibition compared to young adults. Bimanual task performance of older subjects was not worse than ipsilateral hand-foot task performance and did not correlate with cortical inhibition measures, supporting the hypothesis that the increase of ipsilateral activation is not a compensation mechanism.
| Item Type: | Thesis (Thesis) |
|---|---|
| Supervisor name: | Zijdewind, Dr. C.A.T. and Department of Neuroscience, University and Medical Centre Groningen |
| Faculty: | Medical Sciences |
| Date Deposited: | 25 Jun 2020 11:00 |
| Last Modified: | 25 Jun 2020 11:00 |
| URI: | https://umcg.studenttheses.ub.rug.nl/id/eprint/2038 |
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