Elsevier

Biological Psychiatry

Volume 79, Issue 10, 15 May 2016, Pages 823-830
Biological Psychiatry

Archival Report
Frontal Cortex Stimulation Reduces Vigilance to Threat: Implications for the Treatment of Depression and Anxiety

https://doi.org/10.1016/j.biopsych.2015.06.012Get rights and content

Abstract

Background

The difficulty in treating mood disorders has brought about clinical interest in alternative treatments, such as transcranial direct current stimulation (tDCS) of the dorsolateral prefrontal cortex (DLPFC). However, the optimal parameters for stimulation and underlying mechanisms of action are unclear. Psychiatric treatments have acute effects on emotional processing that predict later therapeutic action. Such effects have been proposed as cognitive biomarkers for screening novel treatments for depression and anxiety.

Methods

This study assessed the effect of tDCS on a battery of emotional processing measures sensitive to antidepressant action. To refine optimal stimulation parameters, DLPFC stimulation using two common electrode montages was compared with sham. Sixty healthy volunteers received 20 minutes of active or sham DLPFC stimulation before completing computerized emotional processing tasks, including a dot-probe measure of vigilance to threat.

Results

Relative to sham stimulation, participants receiving simultaneous anodal stimulation of left DLPFC and cathodal stimulation of right DLPFC (bipolar-balanced montage) showed reduced vigilance to threatening stimuli. There was no such significant effect when the cathode was placed on the supraorbital ridge (bipolar-unbalanced montage). There were no effects of tDCS on other measures of emotional processing.

Conclusions

Our findings provide the first experimental evidence that modulating activity in the DLPFC reduces vigilance to threatening stimuli. This significant reduction in fear vigilance is similar to that seen with anxiolytic treatments in the same cognitive paradigm. The finding that DLPFC tDCS acutely alters the processing of threatening information suggests a potential cognitive mechanism that could underwrite treatment effects in clinical populations.

Section snippets

Participants

Ethical approval was obtained from the University of Oxford Central University Ethics Committee (MSD-IDREC-C1-2013-03CUREC). Sixty healthy participants (aged 18–45, 30 female participants) were recruited (see the Supplement for more details).

Design

This study used a between-groups double-blind design with three groups of 20 participants randomized to each condition (active bipolar-balanced DLPFC tDCS, active bipolar-unbalanced DLPFC tDCS, or sham tDCS) with the sham condition randomized across both

Group Matching

The groups did not differ in terms of gender, age, highest education level, personality profile, and baseline mood questionnaire measures (see Table 1 and the Supplement).

Questionnaire Based Measurements

Transcranial direct current stimulation did not significantly affect the mood questionnaire measures (see Table 1 and Supplemental Information).

Behavioral Measurements

Transcranial direct current stimulation did not significantly alter facial expression recognition, emotional categorization, or emotional memory (Supplement).

Faces Dot-Probe Tasks.

Discussion

These findings provide the first experimental evidence that modulating activity in the DLPFC leads to reduced vigilance to threatening stimuli. This study is also the first to directly compare the two most common electrode montages used for DLPFC tDCS, with the results favoring the bipolar-balanced montage. In this study, the group receiving sham stimulation displayed the expected attentional bias toward fearful faces on short stimulus duration trials. Healthy participants typically show this

Acknowledgments and Disclosures

MI is supported by a Medical Research Council studentship and research support grant.

MI and JO report no biomedical financial interests or potential conflicts of interest. PJC has acted as a paid advisor for Lundbeck. CJH has received consultancy income from P1vital, Lundbeck, and Servier. She is a director of Oxford Psychologists Ltd. and holds shares in the company.

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