The differential effects of unihemispheric and bihemispheric tDCS over the inferior frontal gyrus on proactive control

This study examined the effects of bihemispheric and unihemispheric transcranial Direct Current Stimulation (tDCS) over the inferior frontal gyrus (IFG) on proactive control. Sixteen participants were randomized to receive (i) bihemispheric tDCS, with a 35cm2 anodal electrode of the right IFG and a 35cm2 cathode electrode of left IFG or (ii) unihemispheric tDCS, with a 35cm2 anodal electrode of the right IFG and a 100cm2 electrode of the left IFG or (iii) sham tDCS, while performing a prepotent inhibition task. There were significant speed-accuracy tradeoff effects in terms of switch costs: unihemispheric tDCS significantly decreased the accuracy when compared to bihemispheric, and sham tDCS, while increased response time when comparing to bihemispheric and sham tDCS. The computational model showed a symmetrical field intensity for the bihemispheric tDCS montage, and an asymmetrical for the unihemispheric tDCS montage. This study confirms that unihemispheric tDCS over the rIFG has a significant impact on response inhibition. The lack of results of bihemispheric tDCS brings two important findings for this study: (i) left IFG seems to be also critically associated with inhibitory response control, and (ii) these results highlight the importance of considering the dual effects of tDCS when choosing the electrode montage.
JL, SC, OFG are members of CIPSi, supported by the Portuguese
Foundation for Science and Technology and the Portuguese Ministry
of Science, Technology and Higher Education through national
funds and co-financed by FEDER through COMPETE2020 under the
PT2020 Partnership Agreement (POCI-01-0145-FEDER-007653);
and also through the Portuguese Foundation for Science and
Technology PTDC/MHC-PCN/3950/2014. FF is funded by the following
NIH grants: R21HD079048, R01HD082302, 1R44NS080632-01,
1R44AT008637, HD069776. SC is funded by the following Portuguese
Fondation for Science and Technology (FCT) grant
IF/00091/2015.
info:eu-repo/semantics/publishedVersion