Synergistic effects of simultaneous transcranial direct current stimulation (tDCS) and transcutaneous auricular vagus nerve stimulation (taVNS) on the brain responses

Assessing the Effect of Simultaneous Combining of Transcranial Direct Current Stimulation and Transcutaneous Auricular Vagus Nerve Stimulation on the Improvement of Working Memory Performance in Healthy Individuals

“…To the best of our knowledge, this is the first study to explore the synergistic effects of tDCS and taVNS on WM performance and provides the evidence showing the SJS technique to be more effective than anodal tDCS for enhancing WM performance in healthy adults. The results of the current study are partly consistent with those of our previous research (Sun et al, 2021b ), which found that SJS could evoke extensive activation in multiple brain networks, and in several regions, the activation effects were even stronger than those in the numerical summation of the activation by tDCS and taVNS. Recently, peripheral nerve arousal and vigilance were proposed as another possible and important mechanism of tDCS (van Boekholdt et al, 2021 ).…”

“…First, we replicated the positive effects of taVNS on spatial 3-back task accuracy in our previous studies (Sun et al, 2021a ), while no significant results were found in the tDCS group. However, when delivered using the common stimulation parameters (Sun et al, 2021a , b ), we found that combining tDCS over the left or right DLPFC and taVNS, and single taVNS could significantly improve spatial 3-back WM task accuracy, whereas no significant cognitive effects were observed following anodal tDCS over the left or right DLPFC, or sham stimulation. Moreover, SJS induced more consistent improvements in WM accuracy than tDCS, taVNS, or their numerical summation effects.…”

“…A recent brain imagining study has found that combining tDCS and taVNS induced significantly larger activation on a range of cortical and subcortical brain regions than the numerical summation of tDCS and taVNS effects, including the bilateral thalamus, pallidum, parahippocampal gyrus, dorsal raphe nucleus, substantia nigra, and periaqueductal gray matter (Sun et al, 2021b ). Nevertheless, their synergistic effects on cognitive abilities, especially on WM, are still unknown.…”

Transcutaneous Auricular Vagus Nerve Stimulation Improves Spatial Working Memory in Healthy Young Adults

“…Besides, the high baseline of correct rejections might restrict the increased potential of posttest, and the improved familiarity of the tasks leads to a comprehensive main effect of aRT in all groups. However, as shown in the meta-analysis, tDCS could improve the reaction time in healthy adults ( Hill et al, 2016 ); the synergistic effects of tDCS and taVNS might lead to a more comprehensive improvement in WM, which has been proven in neuroimaging study ( Sun et al, 2021 ), whereas the effects on behavior need to be investigated in the future. Another interesting finding that should be noted is that the offline ES increased participants’ correct rejection rate.…”

“…The electrical stimulation equipment used in this study was made by our joint laboratory (XD-Kerfun BS-VNS-001), an upgrade version of the one that has been successfully used in previous researches (e.g., Shen et al, 2021 ; Sun et al, 2021 ). The taVNS channel was connected to two silver chloride electrodes (outer diameter 7 mm).…”