Induction of mirror-touch synaesthesia by increasing somatosensory cortical excitability

Figure 1. Induction of mirror-touch synaesthesia by transcranial electrical stimulation. (A) An incongruent visuo-tactile (VT) trial of the Hand task. The task (~6 min) was to report the site of the actual touch on the hand, while ignoring the viewed touch at the same (Congruent VT) or opposite location (Incongruent VT). In counterbalanced sessions, anodal or sham tDCS (1.5 mA, ~16 min) to S1 or PM of both hemispheres was delivered with a pair of surface electrodes (Red electrode = anodal, blue electrode = reference). (B) The graph depicts the tDCS effect on reaction times in visuo-tactile trials in the Hand task only, highlighted by the Task by tDCS by Side by Stimulus interaction (P < 0.0001). Error bars = S.E. (C) Correlation scatterplots (P < 0.01) for the subjective synaesthetic feeling of being touched during the Hand task (abscissa) from the Questionnaire of Mirror Touch Synaesthesia (QMTS), and (D) for the IRI’s Perspective Taking subscale (abscissa), displaying the S1-tDCS effect in the Hand task (ordinate, Incongruent/Congruent VT difference; positive values, slower responses in incongruent trials). Induction of mirrortouch synaesthesia by increasing somatosensory cortical excitability