Limitation
While this study has several strengths, such as a well-powered within-subjects design and the measurement of various parasympathetic indicators, it is important to acknowledge and address some notable limitations. First, a measure of the sympathetic activity was not evaluated. Therefore, we were not able to investigate how tDCS, via increasing parasympathetic control, can affect the sympathetic nervous system. Second, the neuronavigation method used here was based on a predetermined MRI coordinate. Perhaps, applying individualized DLPFC location based on functional MRI targeting (Cash et al., 2021) may be a further improvement for future studies. Third, due to the within-subject design, blinding was not assessed as it could increase participants’ awareness applying individualized DLPFC location regarding the intervention protocol in the subsequent session.