title: Frontal Cortex Stimulation Reduces Vigilance to Threat: Implications for the Treatment of Depression and Anxiety.
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.
authors.affiliation: Department of Psychiatry, University of Oxford, Oxford, United Kingdom. Electronic address: maria.ironside@psych.ox.ac.uk.
authors.forename: Maria
authors.initials: M
authors.lastname: Ironside
authors.affiliation: Centre for Functional Magnetic Resonance Imaging of the Brain, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom.
authors.forename: Jacinta
authors.initials: J
authors.lastname: O'Shea
authors.affiliation: Department of Psychiatry, University of Oxford, Oxford, United Kingdom.
authors.forename: Philip J
authors.initials: PJ
authors.lastname: Cowen
authors.affiliation: Department of Psychiatry, University of Oxford, Oxford, United Kingdom.
authors.forename: Catherine J
authors.initials: CJ
authors.lastname: Harmer
mesh_terms: D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D001007:Anxiety / Q000503:physiopathology / Q000628:therapy*; D001288:Attention / Q000502:physiology; D003863:Depression / Q000503:physiopathology / Q000628:therapy*; D004311:Double-Blind Method; D004644:Emotions / Q000502:physiology; D005260:Female; D005625:Frontal Lobe / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D011930:Reaction Time; D011795:Surveys and Questionnaires; D065908:Transcranial Direct Current Stimulation / Q000379:methods; D055815:Young Adult
keywords: Anxiety; Cognitive biases; Depression; Emotional processing; Noninvasive brain stimulation; tDCS