Effects of transcranial direct current stimulation over the posterior parietal cortex on tactile spatial discrimination.

The posterior parietal cortex (PPC) plays an important role in discriminating tactile spatial information. Dual-hemisphere transcranial direct current stimulation (tDCS) is a noninvasive and powerful method that can alter cortical excitability. Therefore, the effect of dual-hemisphere tDCS over the PPC on tactile spatial discrimination performance was investigated using the right index finger of 25 participants with normal neurology. The grating orientation discrimination task was performed before, during, and immediately after delivering dual-hemisphere tDCS or unilateral-hemisphere tDCS over the PPC. For dual-hemisphere tDCS, anodal tDCS was applied to the right PPC and cathodal tDCS to the left PPC. Results showed that the effect of dual-hemisphere tDCS and anodal tDCS over the PPC on tactile discrimination performance was significantly higher than sham stimulation. Furthermore, a significant negative correlation was observed between the pre-stimulation tactile discrimination performance and the change in tactile discrimination performance. In conclusion, the stimulatory effect of dual-hemisphere and anodal tDCS over the PPC on tactile discrimination of the right index finger was greater than that of sham stimulation. The effect of both stimulation regimes was associated with baseline tactile discrimination performance.