Fig. 2

Schematic illustration of the placement of the surface electrode for conducting median nerve stimulation at the left wrist. Electrical stimulation was delivered via a fixed bipolar surface electrode (with an interelectrode distance of 23 mm) placed over the course of the median nerve at the wrist. The cathode (−, red) was positioned proximally and the anode (+, black) was positioned distally. The wrist orientation (R ↔ U) indicates the radial (R) and ulnar (U) sides. The stimulation parameters were set to a 7-Hz frequency, a 0.2-ms pulse width, and an approximately 2.5-mA amplitude, adjusted to evoke a clear but comfortable motor response (thumb twitch).