The Long-Term Potentiation-Like Effect in the Corticomotor Area after Transcranial Direct Current Stimulation with Motor Imagery

Abstract

The purpose of the present study was to clarify a long-term potentiation like effect in the corticomotor area after anodal transcranial direct current stimulation (tDCS), which had been done with motor imagery. Anodal tDCS was applied transcranially as an intervention to the left hand motor area in the right hemisphere for 15 min with the intensity of 1.0 mA during resting or motor imagery (MI) conditions. In the MI condition, subjects performed motor imagery of index finger abduction. Motor-evoked potentials (MEPs) were recorded from the first dorsal interossei (FDI) of the left hand before the intervention and at 0 min, 15 min, 30 min and 60 min after the intervention. The stimulus intensities of TMS were set at 1.05, 1.15, and 1.25 times the strength of the resting motor threshold (RMth). Increases of MEPs were detected with all intensities of TMS at 0 min and 15 min after tDCS with motor imagery. However, in the resting condition, MEP amplitudes were elevated only at 15 min after tDCS and at the highest TMS intensity of 1.25×RMth. The facilitatory effect induced by tDCS with motor imagery was significantly long-lasting and definite compared to that after tDCS without motor imagery.