Establishing differences in intracortical inhibition and excitation between individuals with and without stroke
Date
2013
Authors
Vaughn, Heather Noelle, author
Greene, David, advisor
Malcolm, Matt, committee member
Davalos, Deana, committee member
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Abstract
Background and purpose: Even though there is much information and research on neuroplasticity, many questions remain unanswered about how the brain changes and recovers after a stroke. Transcranial magnetic stimulation (TMS) has been used as the primary method of direct stimulation to assess change especially in the primary motor cortex because it allows for study of the specific excitatory and inhibitory mechanisms. The purpose of this study was to investigate and identify differences in TMS-induced intracortical inhibition and facilitation when comparing survivors of stroke to individuals unaffected by stroke. Methods: Fourteen subjects who had experienced a stroke and 19 non-stroke subjects were investigated using single and paired-pulse TMS. TMS was applied over the affected hemisphere for subjects with stroke and over the dominant hemisphere of the non-stroke subjects. Resting motor threshold (MT) was established. Forty motor evoked potentials (MEPs) were collected from the first dorsal interosseus muscle, using surface electrodes, for each subject. These were subdivided into 10 trials of single-pulse conditioning stimulus, 10 trials of single-pulse test stimulus (TS), 10 paired-pulse intracortical facilitation (ICF), 10 paired-pulse intracortical inhibition (ICI); the order of stimulation condition for the 40 trials was randomized. Results: The stroke group exhibited significantly higher MT and significantly lower motor evoked potential amplitudes for TS, ICF, and ICI specific trials compared to the group without stroke. Finally, the ratio of ICF to ICI was found to be significantly lower in the stroke group, indicating less facilitation. Conclusion: Overall the affected hemispheres of the participants surviving stroke were found to be significantly less excitable than the dominant hemispheres of the non-stroke participants. These findings and the usefulness of TMS to directly access and assess differences in the brain's baseline excitability following stroke will hopefully add to existing knowledge that informs therapeutic interventions aimed at increasing post-stroke performance in daily activities.
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Subject
intracortical inhibition
transcranial magnetic stimulation
TMS
stroke
intracortical facilitation