Transcranial direct current stimulation of the motor cortex induces distinct changes in thermal and mechanical sensory percepts

ObjectiveThe aim of this single-blinded, complete crossover study was to evaluate the effects of tDCS on thermal and mechanical perception, as assessed by quantitative sensory testing (QST).MethodsQST was performed upon the radial part of both hands of eight healthy subjects (3 female, 5 male, 25–41 years of age). These subjects were examined before and after cathodal, anodal or sham tDCS, applied in a random order. TDCS was administered for 15 min at a 1 mA current intensity, with the active electrode placed over the left primary motor cortex and the reference electrode above the right orbit.ResultsAfter cathodal tDCS, cold detection thresholds (CDT), mechanical detection thresholds (MDT), and mechanical pain thresholds (MPT) significantly increased in the contralateral hand, when compared to the baseline condition.ConclusionsCathodal tDCS temporarily reduced the sensitivity to A-fiber mediated somatosensory inputs.SignificanceImpairment of these somatosensory percepts suggests a short-term suppression of lemniscal or suprathalamic sensory pathways following motor cortex stimulation by cathodal tDCS.