Figure 1. Effect of cathodal transcranial direct current stimulation (tDCS) on resting motor threshold (A) and on motor evoked potentials (MEP amplitude) (B,C) elicited by transcranial magnetic stimulation (TMS).

MEP amplitude is expressed as a percentage of the control unconditioned response; resting motor threshold is expressed as a percentage of control threshold; error bars show s.e.m. Time axis shows minutes after the end of tDCS or sham stimulation; □, tDCS (n = 7 subjects); Δ, sham stimulation (n = 5). *P < 0.05, **P < 0.01 Wilcoxon signed rank test. MEP recordings from a representative subject (C) showing the decrease in MEP amplitude after cathodal tDCS. Each trace is the average of 24 sweeps. t₀ (0 min after tDCS), t₂₀ (20 min after tDCS), t₄₀ (40 min after tDCS), t₆₀ (60 min after tDCS). Note the persistent decrease in MEP amplitude and persistent increase in resting motor threshold after cathodal tDCS but not after sham stimulation.