Comparing the Effect of Various Intensities of Transcranial Direct Current Stimulation on Cognitive Functions in Normal Subjects: A Randomised Clinical Trial

Introduction: Transcranial Direct Current Stimulation (tDCS) is a technique used to regulate neural activity by applying a lowlevel electrical current to specific brain regions. It modulates neuronal excitability and activity without directly inducing action potentials. The effects of tDCS are dependent on the type of current used, with anodal stimulation generally increasing and cathodal stimulation decreasing the excitability of brain cells. Aim: To determine the efficacy of tDCS in improving the dualtask cognitive function. Materials and Methods: This randomised clinical trial was conducted in the Maharishi Markandeswar Institute of Physiotherapy and Rehabilitation, Mullana, Ambala, Haryana, India, a tertiary health care centre, from August 2022 to April 2023. This study was conducted with 32 participants, dividing them into four groups, each receiving a different level of tDCS intensity (0.5 mA for Group A, 1.0 mA for Group B, 1.5 mA for Group C, and 2.0 mA for Group D). The stimulation was applied to the F3 region (active site) and F4 region (control site) of the frontal cortex, following the 10-20 Electroencephalography (EEG) system. Each session lasted 20 minutes and took place three times a week over a period of three weeks. Throughout the study, participants performed dual-task cognitive exercises, and their cognitive function was assessed both before and after the intervention using the Montreal Cognitive Assessment (MoCA) and Trail Making Test (TMT). Finally, data analysis was performed using Statistical Package for Social Sciences (SPSS) 26.0 software. For datasets satisfying the assumptions of parametric testing, a paired t-test was utilised for within-group comparisons, while an One-way Analysis of Variance (ANOVA) test was used to evaluate group variations. Results: It was assessed whether the demographic data and outcome measures followed a normal distribution, using the Shapiro-Wilk test. The analysis showed no statistically significant between-group dfferences in cognitive performance among healthy participants groups exposed to varying intensities of t-DCS. Although slight fluctuations were observed in the mean MoCA and TMT-A and TMT-B scores across different groups, the p-values remained above the standard level of significance (p-value>0.05). This suggests that the different intensities of t-DCS did not produce a statistically significant effect on cognitive function. Conclusion: The present study found no significant differences in cognitive performance across the various tDCS intensity levels, suggesting that the tested parameters may not have a substantial impact on cognitive function in healthy individuals.