The effects of 1 or 2 mA M1 a-tDCS compared to sham tDCS on motor learning
In the present study, we hypothesized that the groups receiving a-tDCS at intensities of 1 and 2 mA would show significant improvements in motor learning compared to the group receiving sham tDCS. The results of our study not only supported this hypothesis, but also revealed significant effects on both online and offline motor learning when compared to the sham group. These findings are consistent with previous studies conducted by Stagg et al. (2009, 2011), which investigated the efficacy of 1 mA M1 a-tDCS in motor learning and demonstrated a facilitative impact on online motor learning (Stagg et al. , 2009; Stagg et al. , 2011). Furthermore, evidence suggests that a-tDCS can enhance motor learning by facilitating offline consolidation effects (Reis et al. , 2009). Additionally, Ciechanski et al. (2017) found that healthy children exhibited increased motor learning and performance following 1 mA M1 a-tDCS compared to sham tDCS, with lasting effects observed up to 6 weeks after stimulation (Ciechanski & Kirton, 2017). Ambrus et al. also found that anodal stimulation increased offline learning (Ambrus et al. , 2012). According to the study by Greeley et al. (2020), the application of 2 mA M1 a-tDCS showed a faster reduction in RT compared to the sham group (Greeley et al. , 2020). Moreover, these individuals showed faster relearning after one year (Greeley et al. , 2020). It seems that 2 mA a-tDCS has broader and longer-lasting effects on corticospinal excitability, making it a more potent modulator of neuronal activity (Batsikadze et al. , 2013; Strube et al. , 2016). Overall, these studies collectively support our findings that a-tDCS at specific intensities can improve both online and offline motor learning outcomes compared to sham stimulation.