Scientific Reports (Jan 2021)

Group and individual level variations between symmetric and asymmetric DLPFC montages for tDCS over large scale brain network nodes

  • Ghazaleh Soleimani,
  • Mehrdad Saviz,
  • Marom Bikson,
  • Farzad Towhidkhah,
  • Rayus Kuplicki,
  • Martin P. Paulus,
  • Hamed Ekhtiari

DOI
https://doi.org/10.1038/s41598-020-80279-0
Journal volume & issue
Vol. 11, no. 1
pp. 1 – 13

Abstract

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Abstract Two challenges to optimizing transcranial direct current stimulation (tDCS) are selecting between, often similar, electrode montages and accounting for inter-individual differences in response. These two factors are related by how tDCS montage determines current flow through the brain considered across or within individuals. MRI-based computational head models (CHMs) predict how brain anatomy determines electric field (EF) patterns for a given tDCS montage. Because conventional tDCS produces diffuse brain current flow, stimulation outcomes may be understood as modulation of global networks. Therefore, we developed a network-led, rather than region-led, approach. We specifically considered two common “frontal” tDCS montages that nominally target the dorsolateral prefrontal cortex; asymmetric “unilateral” (anode/cathode: F4/Fp1) and symmetric “bilateral” (F4/F3) electrode montages. CHMs of 66 participants were constructed. We showed that cathode location significantly affects EFs in the limbic network. Furthermore, using a finer parcellation of large-scale networks, we found significant differences in some of the main nodes within a network, even if there is no difference at the network level. This study generally demonstrates a methodology for considering the components of large-scale networks in CHMs instead of targeting a single region and specifically provides insight into how symmetric vs asymmetric frontal tDCS may differentially modulate networks across a population.