No interaction between tDCS current strength and baseline performance: a conceptual replication

Learmonth, G. , Felisatti, F., Siriwardena, N., Checketts, M., Benwell, C. S.Y., Märker, G., Thut, G. and Harvey, M. (2017) No interaction between tDCS current strength and baseline performance: a conceptual replication. Frontiers in Neuroscience, 11, 664. (doi: 10.3389/fnins.2017.00664) (PMID:29249932) (PMCID:PMC5717015)

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Several recent studies have reported non-linear effects of transcranial direct current stimulation (tDCS), which has been attributed to an interaction between the stimulation parameters (e.g., current strength, duration) and the neural state of the cortex being stimulated (e.g., indexed by baseline performance ability, age) (see Fertonani and Miniussi, 2016). We have recently described one such non-linear interaction between current strength and baseline performance on a visuospatial attention (landmark) task (Benwell et al., 2015). In this previous study, we induced a small overall rightward shift of spatial attention across 38 participants using bi-hemispheric tDCS applied for 20 min (concurrent left posterior parietal (P5) anode and right posterior parietal (P6) cathode) relative to a sham protocol. Importantly, this shift in bias was driven by a state-dependent interaction between current intensity and the discrimination sensitivity of the participant at baseline (pre-stimulation) for the landmark task. Individuals with high discrimination sensitivity (HDS) shifted rightward in response to low- (1 mA) but not high-intensity (2 mA) tDCS, whereas individuals with low discrimination sensitivity (LDS) shifted rightward with high- but not low-intensity stimulation. However, in Benwell et al. (2015) current strength was applied as a between-groups factor, where half of the participants received 1 mA and half received 2 mA tDCS, thus we were unable to compare high and low-intensity tDCS directly within each individual. Here we aimed to replicate these findings using a within-group design. Thirty young adults received 15 min of 1 and 2 mA tDCS, and a sham protocol, each on different days, to test the concept of an interaction between baseline performance and current strength. We found no overall rightward shift of spatial attention with either current strength, and no interaction between performance and current strength. These results provide further evidence of low replicability of non-invasive brain stimulation protocols, and the need for further attempts to replicate the key experimental findings within this field.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Thut, Professor Gregor and Learmonth, Dr Gemma and Harvey, Professor Monika and Checketts, Mr Matthew and Benwell, Mr Christopher
Authors: Learmonth, G., Felisatti, F., Siriwardena, N., Checketts, M., Benwell, C. S.Y., Märker, G., Thut, G., and Harvey, M.
College/School:College of Medical Veterinary and Life Sciences > School of Psychology & Neuroscience
College of Science and Engineering > School of Psychology
Journal Name:Frontiers in Neuroscience
ISSN (Online):1662-453X
Copyright Holders:Copyright © 2017 Learmonth, Felisatti, Siriwardena, Checketts, Benwell, Märker, Thut and Harvey
First Published:First published in Frontiers in Neuroscience 11(664)
Publisher Policy:Reproduced under a Creative Commons License

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
597911Natural and modulated neural communication: State-dependent decoding and driving of human Brain OscillationsGregor ThutWellcome Trust (WELLCOTR)098434/Z/12/ZINP - CENTRE FOR COGNITIVE NEUROIMAGING