Abstract
Previous language production studies targeting the inferior frontal and superior temporal gyrus using anodal tDCS have provided mixed results. Part of this heterogeneity may be explained by limited target region focality of conventionally used electrode montages. We examined the focality of conventionally and alternative electrode montages. Electrical field distributions of anodal tDCS targeting IFG and pSTG were simulated in conventional setups (anodal electrode over left IFG/pSTG, reference electrode over right supraorbital region) and an alternative electrode montage in four different brains. Conventional montages showed maximum field strengths outside of the target regions. Results from alternative electrode montages showed that focality of tDCS could be improved by adjustments in electrode placement. Heterogeneity of findings of language production studies deploying conventional montages may in part be explained by diffuse electrical field distributions. Alternative montages may improve focality and provide more unequivocal results.
Highlights
In studies on the functional neuroanatomy of language production transcranial direct current stimulation is routinely administered over the left inferior frontal gyrus (IFG) or posterior superior temporal gyrus in healthy volunteers
The goal of the present study was to (1) provide an estimate of the electrical field distributions of the two most commonly used electrode montages targeting the IFG and posterior superior temporal gyrus (pSTG) in language production transcranial direct current stimulation (tDCS) studies, and (2) to present alternative ways to optimize the use of tDCS in language production studies
That these values refer to field strengths observed anywhere in the brain and do not speak to the question which electrical fields are elicited in the target regions
Summary
In studies on the functional neuroanatomy of language production transcranial direct current stimulation (tDCS) is routinely administered over the left inferior frontal gyrus (IFG) or posterior superior temporal gyrus (pSTG) in healthy volunteers. Results of these non-invasive brain stimulation studies have been subject to a significant degree of variability. Meta-analyses on the ability of tDCS to modulate language performance in healthy volunteers have reported small or no effects [12,13,14,15]. Even though these montages have demonstrated the potential to be effective in manipulating processes underlying
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