Transcranial direct current stimulation (tDCS) is a neuromodulatory technique that delivers low-intensity direct current to cortical areas, thereby facilitating or inhibiting spontaneous neuronal activity. This study was designed to investigate changes in various sensory functions after tDCS. We conducted a single-center, single-blinded, randomized trial to determine the effect of a single session of tDCS with the current perception threshold (CPT) in 50 healthy volunteers. Nerve conduction studies were performed in relation to the median sensory and motor nerves on the dominant hand to discriminate peripheral nerve lesions. The subjects received anodal tDCS with 1 mA for 15 minutes under two different conditions, with 25 subjects in each groups: the conditions were as follows tDCS on the primary motor cortex (M1) and sham tDCS on M1. We recorded the parameters of the CPT a with Neurometer(R) at frequencies of 2000, 250, and 5 Hz in the dominant index finger to assess the tactile sense, fast pain and slow pain, respectively. In the test to measure CPT values of the M1 in the tDCS group, the values of the distal part of the distal interphalangeal joint of the second finger statistically increased in all of 2000 Hz (p=.000), 250 Hz (p=.002), and 5 Hz (p=.008). However, the values of the sham tDCS group decreased in all of 2000 Hz (p=.285), 250 Hz (p=.552), and 5 Hz (p=.062), and were not statistically significant. These results show that M1 anodal tDCS can modulate sensory perception and pain thresholds in healthy adult volunteers. The study suggests that tDCS may be a useful strategy for treating central neurogenic pain in rehabilitation medicine.

Purpose: The purpose of this study was to investigate the role of the dorsal premotor cortex (dPMC) in reconstruction and learning of novel finger movement sequence. Especially, different structures of practice (blocked vs. random) were introduced to vary the level of contextual interference, and the dPMC activities during the motor preparation phase were manipulated by the transcranial magnetic stimulation (TMS). Methods: Different patterns of serial key press learning tasks were introduced in random or blocked orders while either the real or the sham TMS was applied at the movement preparation stage. Thus, 56 subjects were randomly assigned into Sham-blocked, TMS-Blocked, Sham-random, and TMS-random practice conditions. 3-way ANOVA were performed to identify the group and condition differences. Results: As a result, the Blocked practice group showed fluent task performances regardless of TMS stimulation during the practice periods, while only the Sham-random practice groups showed the effect of contextual interference in the transfer and retention periods. Conclusion: Significant difference of practice effect depended on the presence of TMS stimulation only with the higher contextual interference in the motor preparation stage. The dPMC seems to be responsible for preparation and reorganization of new motor plans when the variability of the task is high. These results supports the forgetting-reconstruction theory to better explain the effect of contextual interference.