Changes in excitability of cortical projections to the tibialis anterior induced by concurrent motor imagination and peripheral electrical stimulation

Nielsen, Johnny L. G. ; Holmgaard, Steffen

4. term

Biomedical Engineering and Informatics, Master

2009

41

Efter et slagtilfælde kan hjernens motoriske cortex ændre sig (plasticitet), hvilket kan støtte funktionel bedring. Denne undersøgelse afprøvede en ny måde at påvirke, hvor let hjernens forbindelser til skinnebensmusklen tibialis anterior (TA) aktiveres, ved at kombinere mental forestilling om at løfte foden (dorsalfleksion) med kortvarig elektrisk stimulation af den fælles peroneusnerve i underbenet. Vi antog, at effekten afhænger af, hvornår stimulationen når hjernen under den mentale bevægelsesproces. For hver deltager målte vi det bevægelsesrelaterede kortikale potentiale (MRCP), et hjernesignal der stiger før og under bevægelse, for at time stimulationen præcist. I tre separate sessioner blev stimulationen parret med den forestillede bevægelse, så den nåede hjernen (1) i forberedelsesfasen (INT1), (2) i udførelsesfasen (INT2) eller (3) efter udførelsen (INT3). Før og efter hver session registrerede vi motor-evokerede potentialer (MEP'er) i TA—elektriske svar i musklen, når motorsystemet aktiveres—og sammenlignede deres størrelse. På tværs af deltagere steg MEP'erne mest i INT1 (ca. 143 %), mindre i INT2 (ca. 118 %) og kun svagt i INT3 (ca. 107 %). Dette støtter ideen om, at hjernens tilstand (forberedelse versus udførelse) er vigtig for effekten, selv om resultaterne varierede mellem personer. Test tydede på, at ændringerne ikke skyldtes mekanismer i rygmarven, og der sås ingen betydende ændringer i MEP-størrelsen i den modsatvirkende muskel. Fundene peger på en lovende, tidsfølsom tilgang, som kan inspirere nye rehabiliteringsstrategier, men der er behov for yderligere forskning med flere deltagere for at bekræfte resultaterne.

After stroke, the brain’s motor cortex can adapt (plasticity), which may support recovery. This study tested a new way to adjust how readily the brain pathways to the shin muscle tibialis anterior (TA) become active by combining imagined foot lifting (dorsiflexion) with brief electrical stimulation of the common peroneal nerve in the lower leg. We hypothesized that the effect depends on when the stimulation reaches the brain during the mental process of movement. For each participant, we measured the movement-related cortical potential (MRCP), a brain signal that rises before and during movement, to time the stimulation precisely. In three separate sessions, stimulation was paired with the imagined movement so it reached the brain (1) during the preparation phase (INT1), (2) during the execution phase (INT2), or (3) after execution (INT3). Before and after each session, we recorded motor-evoked potentials (MEPs) in TA—electrical responses in the muscle when the motor system is activated—and compared their size. Across participants, MEPs increased most in INT1 (about 143%), less in INT2 (about 118%), and only slightly in INT3 (about 107%). This pattern supports the idea that the brain’s state (preparation versus execution) matters for the effect, though results varied across individuals. Tests suggested the changes were not due to spinal mechanisms, and there were no significant changes in the antagonist muscle’s MEP size. These findings point to a promising, timing-sensitive approach that could inform new rehabilitation strategies, but more research with additional participants is needed to confirm the results.

[This abstract was generated with the help of AI]

EEG ; Cortical plasticity ; Motor imagination ; Hebbian learning

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