Improvement of spatial tactile acuity by transcranial direct current stimulation

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 (tDCS(anodal)) applied to the primary somatosensory cortex (S1) can lead to behavioral changes in performance of tactile discriminative tasks.

Using an accurate tactile discrimination task (grating orientation task: GOT) we tested the hypothesis that application of 1mA of tDCS(anodal) (current density at the electrodes of 0.04mA/cm2) over the left S1 can lead to an improved tactile spatial acuity in the contralateral index-finger (IF).

Performance in the GOT task with the contralateral IF but not with the ipsilateral IF was enhanced for about 40min after a 20min application of tDCS(anodal) in the absence of changes with sham stimulation.

These results provide the first evidence that tDCS(anodal) over S1 improves performance in a complex somatosensory task beyond the period of stimulation.

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.