The effects of bi-hemispheric M1-M1 transcranial direct current stimulation on primary motor cortex neurophysiology and metabolite concentration

Sara Tremblay, Louis Philippe Lafleur, Sébastien Proulx, Vincent Beaulé, Alex Latulipe-Loiselle, Julien Doyon, Magorzata Marjaska, Hugo Théoret

Research output: Contribution to journalArticlepeer-review

8 Scopus citations

Abstract

Purpose: The aim of the present study was to assess, in healthy individuals, the impact of M1-M1 tDCS on primary motor cortex excitability using transcranial magnetic stimulation and sensorimotor metabolite concentration using 1H-MRS. Methods: For both experiments, each participant received the three following interventions (20 min tDCS, 1 mA): left-anodal/right-cathodal, left-cathodal/right-anodal, sham. The effects of tDCS were assessed via motor evoked potentials (experiment 1) and metabolite concentrations (experiment 2) immediately after and 12 minutes following the end of stimulation and compared to baseline measurement. Results: No effect of M1-M1 tDCS on corticospinal excitability was found. Similarly, M1-M1 tDCS did not significantly modulate metabolite concentrations. High inter-subject variability was noted. Response rate analysis showed a tendency towards inhibition following left-anodal/right-cathodal tDCS in 50 of participants and increased GABA levels in 45 of participants. Conclusion: In line with recent studies showing important inter-subject variability following M1-supraorbital tDCS, the present data show that M1-M1 stimulation is also associated with large response variability. The absence of significant effects suggests that current measures may lack sensitivity to assess changes in M1 neurophysiology and metabolism associated with M1-M1 tDCS.

Original languageEnglish (US)
Pages (from-to)587-602
Number of pages16
JournalRestorative Neurology and Neuroscience
Volume34
Issue number4
DOIs
StatePublished - Aug 13 2016

Keywords

  • GABA
  • Magnetic resonance spectroscopy
  • glutamate
  • motor cortex
  • transcranial direct current stimulation

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