Voluntary movement reverses the effect of cathodal transcranial direct current stimulation (tDCS) on corticomotor excitability

Ataoglu E. E., BATUR ÇAĞLAYAN H. Z., CENGİZ B.

EXPERIMENTAL BRAIN RESEARCH, vol.235, no.9, pp.2653-2659, 2017 (SCI-Expanded) identifier identifier identifier

  • Publication Type: Article / Article
  • Volume: 235 Issue: 9
  • Publication Date: 2017
  • Doi Number: 10.1007/s00221-017-5001-9
  • Journal Name: EXPERIMENTAL BRAIN RESEARCH
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.2653-2659
  • Keywords: Transcranial direct current stimulation, Transcranial magnetic stimulation, Corticomotor excitability, Voluntary movement, Motor evoked potential, PRIMARY MOTOR CORTEX, HOMEOSTATIC PLASTICITY, MAGNETIC STIMULATION
  • Gazi University Affiliated: Yes

Abstract

Motor cortex activity level is a critical part of the effect of transcranial direct current stimulation (tDCS) on corticomotor excitability. Based on homeostatic plasticity, the state of the stimulated cortical area influences the direction of neuroplastic changes induced by stimuli. Owing to homeostatic plasticity, cathodal tDCS (c-tDCS) would likely have a pronounced inhibitory effect on corticomotor excitability during a motor task, compared with the resting state. To test this hypothesis, we detected motor evoked potential (MEP) amplitude changes before and during c-tDCS with voluntary movement. Twelve healthy right-handed volunteers (9 males, 27-48 years) were enrolled in the study. Subjects performed little finger abduction motor task. Passive (APB) and active (ADM) muscles were studied. MEP amplitudes were measured during resting (baseline) and movement stages, and subsequently with the contralateral M1 modulated by c-tDCS. c-tDCS caused reduced baseline MEP amplitude in the ADM (p < 0.05) and APB (p < 0.001) muscles. Sham stimulation had no effect on the baseline MEP amplitudes. MEP amplitude ratio (MEP amplitude (triggered by movement)/baseline MEP amplitude) was higher during c-tDCS than before c-tDCS (p < 0.01). Our results suggested that during voluntary contraction, c-tDCS has an opposite effect on corticospinal excitability compared with resting state modulation effect. This contrast effect could be related to modulation of movement preparation and execution.