Impact of Anodal and Cathodal Transcranial Direct Current Stimulation over the Left Dorsolateral Prefrontal Cortex during Attention Bias Modification: An Eye-Tracking Study.

Alexandre Heeren,Pierre Philippot,Rudi De Raedt,Marie-Anne Vanderhasselt,Chris Baeken

doi:10.1371/journal.pone.0124182

Alexandre Heeren, Pierre Philippot + Show 3 more

Open Access

https://doi.org/10.1371/journal.pone.0124182

Copy DOI

Abstract

People with anxiety disorders show an attentional bias for threat (AB), and Attention Bias Modification (ABM) procedures have been found to reduce this bias. However, the underlying processes accounting for this effect remain poorly understood. One explanation suggests that ABM requires the modification of attention control, driven by the recruitment of the dorsolateral prefrontal cortex (DLPFC). In the present double-blind study, we examined whether modifying left DLPFC activation influences the effect of ABM on AB. We used transcranial direct current stimulation (tDCS) to directly modulate cortical excitability of the left DLPFC during an ABM procedure designed to reduce AB to threat. Anodal tDCS increases excitability, whereas cathodal tDCS decreases it. We randomly assigned highly trait-anxious individuals to one of three conditions: 1) ABM combined with cathodal tDCS, 2) ABM combined with anodal tDCS, or 3) ABM combined with sham tDCS. We assessed the effects of these manipulations on both reaction times and eye-movements on a task indexing AB. Results indicate that combining ABM and anodal tDCS over the left DLPFC reduces the total duration that participants’ gaze remains fixated on threat, as assessed using eye-tracking measurement. However, in contrast to previous studies, there were no changes in AB from baseline to post-training for participants that received ABM without tDCS. As the tendency to maintain attention to threat is known to play an important role in the maintenance of anxiety, the present findings suggest that anodal tDCS over the left DLPFC may be considered as a promising tool to reduce the maintenance of gaze to threat. Implications for future translational research combining ABM and tDCS are discussed.

Highlights

Over the two last decades, evidence has accumulated that individuals who suffer from anxiety disorders, regardless of the type of anxiety, exhibit an attentional bias (AB) for threatening stimuli, concerning impaired disengagement of attention from threat such as angry faces [2,3,4]
The main aim of the present study was to examine the influence of transcranial Direct Current Stimulation (tDCS) over the left dorsolateral prefrontal cortex (DLPFC) during an ABM procedure on AB in a selected sample of highly trait-anxious individuals with eye-tracking measurements
We hypothesized that participants receiving anodal tDCS during the ABM procedure should demonstrate stronger reduction in both reaction time (RT) and EMs indices of AB than those receing sham tDCS

Summary

Introduction

Over the two last decades, evidence has accumulated that individuals who suffer from anxiety disorders, regardless of the type of anxiety, exhibit an attentional bias (AB) for threatening stimuli (for a meta-analysis, see [1]), concerning impaired disengagement of attention from threat such as angry faces [2,3,4]. Researchers have started to investigate the causal nature of these biases in the maintenance of anxiety disorders by directly manipulating AB. Using a modified version of the dot probe paradigm (see Fig 1a), it has been observed that training anxious individuals to attend to non-threat (i.e., attention bias modification; ABM) reduces AB, which, in turn, reduces anxiety [5,6]. These findings support a central tenet of several cognitive models of anxiety disorders, i.e. that information-processing biases may causally maintain the disorders [7]. Several explanations have been proposed to account for the mechanisms underlying such a plasticity of AB and, in turn, its impact on anxiety

Objectives

Results

Conclusion