Figure 2. Box plots of compound muscle action potentials (CMAPs) in the tibialis anterior muscle to single or paired transcranial electrical stimulation. Horizontal bars = 90th, 75th, 50th (median), 25th, and 10th percentiles. The distribution of amplitudes of motor evoked responses to transcranial stimulation (tc-MER) is skewed. *P < 0.01 compared with single-pulse stimulation.