Motor cortex-induced plasticity by noninvasive brain stimulation

Abstract

The aim of this study was to test and compare the effects of a within-subject design of repetitive transcranial magnetic stimulation (rTMS) [coupled with sham transcranial direct current stimulation (tDCS)] and tDCS (coupled with sham rTMS) on the motor cortex excitability and also compare the results against sham tDCS/sham rTMS. We conducted a double-blinded, randomized, sham-controlled, cross-over trial. Eleven right-handed, healthy individuals (five women, mean age: 39.8 years, SD 13.4) received the three interventions (cross-over design) in a randomized order: (a) high-frequency (HF) rTMS (+sham tDCS), (b) anodal tDCS (+sham rTMS), and (c) sham stimulation (sham rTMS+sham tDCS). Cortical excitability measurements [motor threshold, motor evoked potential (MEP), intracortical facilitation and inhibition, and transcallosal inhibition] and motor behavioral assessments were used as outcome measures. Between-group analysis of variance showed that MEP amplitude after HF rTMS was significantly higher than MEP amplitude after anodal tDCS (P=0.001). Post-hoc analysis showed a significant increase in MEP amplitude after HF rTMS (25.3%, P=0.036) and a significant decrease in MEP amplitude after anodal tDCS (-32.7%, P=0.001). There was a similar increase in motor function as indexed by Jebsen-Taylor Hand Function Test in the two active groups compared with sham stimulation. In conclusion, here, we showed that although both techniques induced similar motor gains, they induce opposing results in cortical excitability. HF rTMS is associated with an increase in corticospinal excitability, whereas 20 min of tDCS induces the opposite effect. We discuss potential implications of these results to future clinical experiments using rTMS or tDCS for motor function enhancement.

The Impact of Single Session Intermittent Theta-Burst Stimulation over the Dorsolateral Prefrontal Cortex and Posterior Superior Temporal Sulcus on Adults with Autism Spectrum Disorder

“…One early study demonstrated that the aftereffect of rTMS on compulsive behaviors could be found 8 h afterward (Greenberg et al, 1997). Following studies demonstrated that the effect of one session rTMS does not last for 1 week, and a week interval has been commonly applied to control the residual effect in a within-subject design (Simis et al, 2013; Kim and Shin, 2014; Tard et al, 2016). Based on these findings, we decided to evaluate the changes in behaviors and social symptoms in ASD 8 h and 2 days afterward.…”

Evidence that transcranial direct current stimulation (tDCS) generates little-to-no reliable neurophysiologic effect beyond MEP amplitude modulation in healthy human subjects: A systematic review

“…Thirugnanasambandam et al (2011) was excluded from analysis for reporting only percent change (rather than percentage of unconditioned response). Simis et al (2013) was excluded from analysis as they did not supply numerical data (although this paper reported no significant effect of stimulation on either SICI or ICF). Jefferson et al (2009) was excluded from analysis as they did not supply numerical data (although this paper reported no significant effect of stimulation on either SICI or ICF).…”

Possible Mechanisms Underlying the Therapeutic Effects of Transcranial Magnetic Stimulation

“…These effects likely underlie the long-lasting duration of the therapeutic effects of TMS. The effects of rTMS are often stronger than are those of direct electric stimulation, and some changes are only observed following rTMS (Simis et al, 2013). …”