Diagram illustrating the randomization of parameters to be examined in one exemplary subject.

<p>Parameters of motor cortical excitability and function were assessed at two time intervals (early or late) following transcranial direct current stimulation (indicated by a flash symbol). Changes in measures recorded 0–40 minutes after discontinuation of the stimulation were considered to be due to early aftereffects. Changes recorded in the successive 40 minutes were considered to be due to late aftereffects. Aftereffects which occured in only one recording period were considered to be short-lasting; others were considered to be long-lasting. Immediately before and after tDCS, 20 stimuli were applied at a fixed intensity (see methods section for details) over M1 to examine tDCS-induced changes of corticospinal excitability. Afterwards, the five neurophysiological or functional parameters being evaluated were randomly assigned to one of four time slots in the overall 80-minute post-stimulation period. IO = input-output curve, TAP = finger-tapping, ICE = intracortical excitability (Short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF), IHI = interhemispheric inhibition, MT = motor threshold; Pos1 – Pos4: Random position in time for each parameter.