Anodal Transcranial Pulsed Current Stimulation: The Effects of Pulse Duration on Corticospinal Excitability

The aim is to investigate the effects of pulse duration (PD) on the modulatory effects of transcranial pulsed current (tPCS) on corticospinal excitability (CSE). CSE of the dominant primary motor cortex (M1) of right first dorsal interosseous muscle was assessed by motor evoked potentials, before, immediately, 10, 20 and 30 minutes after application of five experimental conditions: 1) anodal transcranial direct current stimulation (a-tDCS), 2) a-tPCS with 125 ms pulse duartion (a-tPCS(PD = 125)), 3) a-tPCS with 250 ms pulse duration (a-tPCS(PD = 250)), 4) a-tPCS with 500 ms pulse duration (a-tPCS(PD = 500)) and 5) sham a-tPCS. The total charges were kept constant in all experimental conditions except sham condition. Post-hoc comparisons indicated that a-tPCS(PD = 500) produced larger CSE compared to a-tPCS(PD = 125) (P<0.0001), a-tPCS(PD = 250) (P = 0.009) and a-tDCS (P = 0.008). Also, there was no significant difference between a-tPCS(PD = 250) and a-tDCS on CSE changes (P>0.05). All conditions except a-tPCS(PD = 125) showed a significant difference to the sham group (P<0.006). All participants tolerated the applied currents. It could be concluded that a-tPCS with a PD of 500ms induces largest CSE changes, however further studies are required to identify optimal values.