Stimulation intensities of transcranial direct current stimulation have to be adjusted in children and adolescents.

Objective: The aim of the present study was to investigate the effect of the transcranial direct current stimulation (tDCS) on motor cortex excitability in healthy children and adolescents.

Methods: We applied 1mA anodal or cathodal tDCS for 10min on the left primary motor cortex of 19 healthy children and adolescents (mean age 13.9±0.4years). In order to prove whether the effects of tDCS may be attributed to the stimulation intensity, 10 children and adolescents were studied again using 0.5mA anodal and cathodal tDCS. Sham stimulation was used as a control.

Results: Compared with sham stimulation, both 1mA anodal and cathodal tDCS resulted in a significant increase of Motor evoked potentials (MEP) amplitudes which remained to be prominent even one hour after the end of stimulation. Interestingly, the 0.5mA cathodal tDCS decreased cortico-spinal excitability whereas the 0.5mA anodal stimulation did not result in any effect.

Conclusion: For the first time, the study demonstrates age-specific influences of tDCS on cortical excitability of the primary motor cortex.

Significance: Thus, the stimulation protocols of the tDCS have to be optimized according to age by planning studies in pediatric population.