Medizinische Universität Graz Austria/Österreich - Forschungsportal - Medical University of Graz
Gewählte Publikation:
Postruznik, M.
Effects of Transcranial Alternating Magnetic Stimulation on Motor Cortex Excitability
Humanmedizin; [ Diplomarbeit ] Graz Medical University; 2017. pp. 64
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- Autor*innen der Med Uni Graz:
- Betreuer*innen:
- Gallasch Eugen
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- Abstract:
- Non-invasive brain stimulation refers to well-known techniques that are able to modulate cortical excitability, such as repetitive transcranial magnetic stimulation (rTMS), transcranial direct current stimulation (tDCS) or transcranial alternating current stimulation (tACS). For this study transcranial alternating magnetic stimulation (tAMS) was tested in order to evoke modulatory changes in motor cortex. The technique consists of a rotating permanent magnet, able to produce a 20 Hz magnetic field with a strength of 0.1 Tesla in motor cortex. Our hypothesis was that the electromagnetic induction as produced by this kind of tAMS, should be strong enough in order to modulate cortical excitability, similar as with tACS. For our study we applied a sham-controlled, double blind cross-over design. We tested 14 right-handed subjects, who underwent three interventions (15 minutes of tACS, tAMS or sham) and we assessed cortical excitability changes via single and paired pulse TMS in pre-post sessions. Furthermore, we assessed possible changes in motor performance by using the grooved pegboard test (GPT) before and after every treatment. The TMS pulses stimulated the motor cortex which lead to a motor evoked potential MEP in the first dorsal interosseus of the right hand. We recorded single pulse MEPs (at intensities 110%, 130% and 150% of resting motor threshold) to assess corticospinal excitability and cortical silent period (CSP), as well as paired pulse MEPs in order to assess short interval intracortical inhibition (SICI) and intracortical facilitation (ICF). The tACS increased the MEP amplitudes at every intensity level (p = 0.001 at 110%, p = 0.000 at 130%, p = 0.001 at 150%), but showed no effect on the other parameters. The tAMS decreased the MEP amplitudes at intensities of 110% (p = 0.015) and 150% (p = 0.018), and lead to a significant decrease of conditioned MEP amplitudes in SICI (p = 0.011) and ICF (p = 0.002). None of the interventions showed significant effects in CSP and GPT performance. Contrary to our hypothesis the tAMS showed a decrease of cortical excitability. Further research will be needed to elucidate the neuronal mechanisms underlying tAMS.