Does the longer application of anodal-transcranial direct current stimulation increase corticomotor excitability further? a pilot study

ABSTRACT

Anodal transcranial direct current stimulation [a-tDCS] of the primary motor cortex [M1] has been shown to be effective in increasing corticomotor excitability. We investigated whether longer applications of a-tDCS coincide with greater increases in corticomotor excitability compared to shorter application of a-tDCS. Ten right-handed healthy participants received one session of a-tDCS [1mA current] with shorter [10 min] and longer [10+10 min] stimulation durations applied to the left m1 of extensor carpi radialis muscle [ECR]. Corticomotor excitability following application of a-tDCS was assessed at rest with transcranial magnetic stimulation [TMS] elicited motor evoked potentials [MEP] and compared with baseline data for each participant. MEP amplitudes were increased following 10 min of a-tDCS by 67% [p=0.001] with a further increase [32%] after the second 10 min of a-tDCS [p =0.005]. MEP amplitudes remained elevated at 15 min post stimulation compared to baseline values by 65% [p=0.02]. The results demonstrate that longer application of a-tDCS within the recommended safety limits, increases corticomotor excitability with after effects of up to 15 minutes post stimulation