Conclusion
This study examined the modulatory effects of different tDCS intensities
on HRV in healthy individuals. The findings support the dose-dependent
effects of tDCS, with the highest electric current intensity (3.0mA)
demonstrating a significant increase in HRV compared to both sham and
1.5mA current. While the individual amount of electric current
penetrating the brain did not appear to significantly influence the tDCS
effects on HRV modulation, E-field modeling analysis suggests that the
heterogeneity of tDCS protocols may contribute to the variability in
tDCS effects on cardiovascular measures. This study highlights the
effects of tDCS on parasympathetic activity of healthy subjects via
prefrontal tDCS, showing a dose-dependent effect. Based on our results,
we believe that further research is warranted to investigate the optimal
tDCS parameters for HRV modulation.
Acknowledgement
LBR is currently supported by a Research Foundation Flanders (FWO) grant
(G0F4619N). RDR and MMP received support from the Research Foundations
FWO and F.R.S.-FNRS under the Excellence of Science (EOS) program (EOS
40007528). MAV received funding from FWO-Flanders for research projects
for fundamental research (Grant Numbers: G044222N; G044019N). ARB
receives grants from the National Council for Scientific and
Technological Development (PQ-1B), and FAPESP (Grants: 2018/10861-7,
2019/06009-6). ARB has a small equity of Flow™, whose devices were not
used in the present study. The LIM-27 laboratory receives grants from
the Associação Beneficente Alzira Denise Hertzog da Silva. SDS is funded
by a FWO-Flanders PhD fellowship (Grant Number: 11J7521N).The other
authors have no conflicts of interest to disclose.