Electrotactile Characteristics of Rectified Random Noise Stimulation (r-tRNS) on the Forehead: A Comparison with tDCS

Electrical stimulation on the forehead has been applied in various technologies, and understanding the electrotactile characteristics induced by stimulation is essential for ensuring safe and efficient applications. Transcranial random noise stimulation (tRNS) has gained increasing attention for its strong neuromodulatory effects and relatively low discomfort compared to other stimulation methods. However, its bidirectional current requires a more complex hardware configuration. In this study, we propose rectified random noise stimulation in the frontal region (r-tRNS), employing a unidirectional current, and compare its electrotactile characteristics with those of transcranial direct current stimulation (tDCS). Thirteen participants underwent electrical stimulation to determine the perception threshold (PT), the minimum intensity at which stimulation is perceived, and the tolerance threshold (TT), the minimum intensity that induces discomfort. The results revealed that r-tRNS demonstrated significantly lower PT and TT values compared to tDCS (p-value < 0.004), suggesting that r-tRNS generates stronger cutaneous sensations than tDCS. These findings indicate that r-tRNS has the potential to be effectively utilized in applications requiring electrotactile perception, such as sensory substitution technologies.Clinical Relevance-This study explores r-tRNS, a novel forehead electrical stimulation method, and its electrotactile characteristics to provide insights for applications such as sensory substitution or electroceuticals.