Figure 5

(A) Experimental design of a single session. In this study we used a double-blind, crossover study design with 2 sessions (tDCS and Sham). Half of the patients started with tDCS and the other half with Sham. Each session started with baseline determinations (BASE) of reaction times (RT_1–3) and pinch force (PF_1–3), followed by a 30 min break in which tDCS electrodes were placed. Then tDCS or Sham was applied in a counterbalanced double-blind design followed by post intervention measures (RT_4–6 and PF_4–6). All patients described their level of attention toward the task (range: 1–10; 1 = no attention, 10 = highest level of attention) and their perception of fatigue (range: 1–10; 1 = highest level of fatigue, 10 = no fatigue) four times in each session (VAS₁-VAS₄), and their sense of discomfort/pain after each session ended (range: 1–10; 1 = no discomfort/pain, 10 = maximal discomfort/pain) using visual analog scales (VAS) that have good internal consistency, reliability, and objectivity [24, 25, 27, 28]. Instructions to the patients were identical for all Sessions. In 4 patients an additional session was performed as a control experiment to evaluate the effects of No Stimulation compared to Sham stimulation. (B) Reaction Time Testing during a Visuo-Motor Task Patients were seated in a comfortable armchair and were instructed to focus attention on a cross in the centre of a video screen, and to bend their wrist as quickly as possible in response to a GO-signal presented on the screen. Trials were started with a visual warning signal ('Get ready'), followed by a GO-signal at random intervals (2–6 seconds). Blocks consisted of 23 wrist flexion trials with the first three trials of a block used as practice trials. These trials were not included in the analysis. EMG was recorded from silver-silver chloride electrodes positioned in a belly tendon montage on the skin overlying the Flexor Carpi Radialis muscle. Reaction times (RT) were defined as the time interval between the GO-signal and the onset of the EMG-burst in the Flexor Carpi Radialis muscle. Patients didn't receive any feedback about there performance. (C) Pinch Force Testing Task Patients were seated in a comfortable armchair with both arms relaxed. Maximal pinch strength of the paretic hand was measured according to a protocol with good validity and test-retest reliability [49, 50]. Patients held the arm of a dynamometer between the lateral aspect of the middle phalanx of the index finger and the thumb pad. Trials were started with a warning signal ('Get ready'), followed by a GO-signal at random intervals (2–6 seconds). Patients were instructed to squeeze the gauge as hard as they could for 1–3 seconds after GO-signal. Patients didn't receive any feedback about there performance. Blocks consisted of nine consecutive trials.