Non-linear effects of transcranial direct current stimulation as a function of individual baseline performance: evidence from biparietal tDCS influence on lateralized attention bias

Benwell, C. S.Y., Learmonth, G., Miniussi, C., Harvey, M. and Thut, G. (2015) Non-linear effects of transcranial direct current stimulation as a function of individual baseline performance: evidence from biparietal tDCS influence on lateralized attention bias. Cortex, 69, pp. 152-165. (doi:10.1016/j.cortex.2015.05.007) (PMID:26073146)

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Abstract

Transcranial direct current stimulation (tDCS) is a well-established technique for non-invasive brain stimulation (NIBS). However, the technique suffers from a high variability in outcome, some of which is likely explained by the state of the brain at tDCS-delivery but for which explanatory, mechanistic models are lacking. Here, we tested the effects of bi-parietal tDCS on perceptual line bisection as a function of tDCS current strength (1 mA vs 2 mA) and individual baseline discrimination sensitivity (a measure associated with intrinsic uncertainty/signal-to-noise balance). Our main findings were threefold. We replicated a previous finding (Giglia et al., 2011) of a rightward shift in subjective midpoint after Left anode/Right cathode tDCS over parietal cortex (sham-controlled). We found this effect to be weak over our entire sample (n = 38), but to be substantial in a subset of participants when they were split according to tDCS-intensity and baseline performance. This was due to a complex, nonlinear interaction between these two factors. Our data lend further support to the notion of state-dependency in NIBS which suggests outcome to depend on the endogenous balance between task-informative ‘signal’ and task-uninformative ‘noise’ at baseline. The results highlight the strong influence of individual differences and variations in experimental parameters on tDCS outcome, and the importance of fostering knowledge on the factors influencing tDCS outcome across cognitive domains.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Learmonth, Dr Gemma and Thut, Professor Gregor and Harvey, Dr Monika
Authors: Benwell, C. S.Y., Learmonth, G., Miniussi, C., Harvey, M., and Thut, G.
College/School:College of Medical Veterinary and Life Sciences > Institute of Neuroscience and Psychology
College of Science and Engineering > School of Psychology
Journal Name:Cortex
Publisher:Elsevier
ISSN:0010-9452
Copyright Holders:Copyright © 2015 The Authors
First Published:First published in Cortex 69:152-165
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 (WELLCOME)098434/Z/12/ZINP - CENTRE FOR COGNITIVE NEUROIMAGING