Anodal transcranial pulsed current stimulation: A novel technique to enhance corticospinal excitability

• Transcranial pulsed current stimulation (tPCS) is a novel non-invasive neuromodulatory paradigm with less side effects compared to the conventional transcranial direct current stimulation (tDCS).
• Despite tDCS which modifies neuronal excitability by tonic depolarization of the resting membrane potential, tPCS modifies neuronal excitability by a combination of tonic and phasic effects.
• tPCS appears to be a promising tool for clinical neuroplasticity research as a new method of delivering transcranial stimulation for modulation of corticospinal excitability.

ObjectiveWe aimed to compare the effects of anodal-transcranial pulsed current stimulation (a-tPCS) with conventional anodal transcranial direct current stimulation (a-tDCS) on corticospinal excitability (CSE) in healthy individuals.MethodsCSE of the dominant primary motor cortex of the resting right extensor carpi radialis muscle was assessed before, immediately, 10, 20 and 30 min after application of four experimental conditions: (1) a-tDCS, (2) a-tPCS with short inter-pulse interval (a-tPCSSIPI, 50 ms), (3) a-tPCS with long inter-pulse interval (a-tPCSLIPI., 650 ms) and (4) sham a-tPCS. The total charges were kept constant in all experimental conditions except sham condition. The outcome measure in this study was motor evoked potentials.ResultsOnly a-tDCS and a-tPCSSIPI (P < 0.05) induced significant increases in CSE, lasted for at least 30 min. Post-hoc tests indicated that this increase was larger in a-tPCSSIPI (P < 0.05). There were no significant changes following application of a-tPCSLIPI and sham a-tPCS. All participants tolerated the applied currents in all experimental conditions very well.ConclusionsCompared to a-tDCS, a-tPCSSIPI is a better technique for enhancement of CSE. There were no sham effects for application of a-tPCS. However, unlike a-tDCS which modifies neuronal excitability by tonic depolarization of the resting membrane potential, a-tPCS modifies neuronal excitability by a combination of tonic and phasic effects.Significancea-tPCS could be considered as a promising neuromodulatory tool in basic neuroscience and as a therapeutic technique in neurorehabilitation.