Implications
COMPLICATION
The ability of tDCS to induce CNS plasticity, measured with, for example, MEPs, fMRI, EEG, and brain derived neurotrophic factor level (Fritsch et al. In the present study, we observed that the excitability of soleus H-reflex pathway was briefly increased by both Active and Sham tDCS applied during standing, and then, its excitability significantly decreased from this brief enhancement. These temporary changes in reflex excitability were not observed in previous reflex studies in which 225–245 reflex trials were administered over 30–40 min period without tDCS (Thompson, et al. Whether the small effects seen here are enough to change a motor behavior is yet to be determined. Many studies already avoid a possible complication shown here with Sham tDCS (i.e., temporary increase of H-reflex excitability) by not beginning the intervention until after the tDCS is turned off, although evidence exists that applying tDCS during practice of novel hand (pinch force) and leg (pattern tracing) motor skills enhance their acquisition (i.e., accuracy and speed) (Reis et al. In sum, future clinical studies that use tDCS as an adjuvant therapy should consider the impact of tDCS on the neural pathway of the targeted behavior (if it is known) and carefully evaluate the effects of their Sham procedures.