Improvement of spatial tactile acuity by transcranial direct current stimulation

Objective Non-invasive brain stimulation such as transcranial direct current stimulation (tDCS) has been successfully used to induce polarity-specific excitability changes in the brain. However, it is still unknown if anodal tDCS (tDCSanodal) applied to the primary somatosensory cortex (S1) can lead to behavioral changes in performance of tactile discriminative tasks. Methods Using an accurate tactile discrimination task (grating orientation task: GOT) we tested the hypothesis that application of 1 mA of tDCSanodal (current density at the electrodes of 0.04 mA/cm2) over the left S1 can lead to an improved tactile spatial acuity in the contralateral index-finger (IF). Results Performance in the GOT task with the contralateral IF but not with the ipsilateral IF was enhanced for about 40 min after a 20 min application of tDCSanodal in the absence of changes with sham stimulation. Conclusions These results provide the first evidence that tDCSanodal over S1 improves performance in a complex somatosensory task beyond the period of stimulation. Significance The ability to induce performance improvement in the somatosensory domain with tDCS applied over S1 could be used to promote functional recovery in patients with diminished tactile perception.