Enhancement of Therapeutic Learning in OCD Using tDCS
Condition: Obsessive-Compulsive Disorder
MeSH terms: Compulsive Personality Disorder; Obsessive-Compulsive Disorder
Study type: Interventional

Summary: 
      Psychiatric disorders characterized by pathological fear and anxiety are common and often
      disabling. Despite their limitations, exposure therapies are among the most efficacious
      treatments for these disorders. Extinction learning is thought to be a core mechanism of
      therapeutic exposure. Extinction learning is mediated by a well-defined circuit encompassing
      the medial prefrontal cortex (mPFC), amygdala, and hippocampus. This raises the exciting
      possibility that direct engagement of this circuitry might enhance the response to
      therapeutic exposure. Transcranial direct current stimulation (tDCS) is a neuromodulation
      technology that can augment brain plasticity, learning, and memory. The proposed study will
      evaluate whether tDCS can improve therapeutic learning and memory processes among
      participants diagnosed with obsessive-compulsive disorder (OCD) This study aims to use tDCS
      to improve learning and memory processes within the context of an exposure laboratory
      challenge. Participants diagnosed with OCD will complete a two-day experimental study. On day
      1, participants will receive sham (placebo) or active tDCS followed by approximately
      50-minutes of individualized exposure. on day 2, participants will return to complete an
      additional 50-minutes of exposure. Subjective distress will be repeatedly monitored during
      exposure to allow for the modeling of within-trail and within-session learning and
      between-session recall of learning.
    

Detailed description: 
      Most effective behavioral treatments of disordered anxiety involve repeated exposure to
      feared stimuli, which often results in systematic reductions in fearful responding to said
      stimuli. It is believed that this process results from successful fear extinction, a
      well-characterized learning process that is mediated by fear extinction brain circuitry.
      Namely, fear extinction is an inhibitory learning process that requires activation and
      plasticity within a variety of brain regions, including the medial prefrontal cortex (mPFC),
      which can exert inhibitory control over fearful responding and parts of the brain that drive
      said responding. Behavioral treatments of disordered anxiety, while effective, have serious
      limitations; many patients fail to respond at all or only partially respond to exposure-based
      treatments. One candidate reason for this is deficits in fear extinction learning or memory
      processes. The proposed study aims to examine the effects of non-invasive neuromodulation -
      namely, multifocal transcranial direct current stimulation (tDCS) targeting the mPFC - on
      therapeutic learning and memory among adults diagnosed with obsessive-compulsive disorder
      (OCD).

      This study will recruit 26 subjects with OCD to complete a two-day experimental protocol to
      examine the effects of tDCS on therapeutic learning and memory, which will be measured with
      an exposure and response prevention laboratory challenge. On Day 1, OCD subjects will be
      randomized (1:1, double-blind) to receive Active (n = 13) or Sham (n = 13) tDCS prior to
      completing five 10-minute in vivo exposure exercises to assess the effects of tDCS on the
      acquisition of therapeutic learning. Subjects and raters (including those directing exposure
      sessions) will be blind to allocation. On Day 2, OCD subjects will return to complete five
      additional exposure trials to examine the effects of tDCS on recall of therapeutic learning.
      Subjective ratings of emotional distress (0-100) will be collected at baseline, before and
      after tDCS, and during each minute of each exposure trial. It is hypothesized that tDCS will
      improve the acquisition and recall of therapeutic learning (Aim 4); that participants
      randomized to Active tDCS would show more rapid reductions in subjective distress and would
      recall therapeutic learning on Day 2 when compared to participants randomized that Sham tDCS.

      tDCS will be delivered using an 8-channel Starstim transcranial electric stimulator from
      Neuroelectrics. To target the mPFC, the anodal electrode will be placed over the frontal pole
      (Fpz, 10-20 EEG landmarks) and will be surrounded by five return (cathodal) electrodes in a
      circumferential array (AF7, AF8, F3, Fz, and F4). Subjects in the Active tDCS condition will
      receive 20 minutes of direct current stimulation for 20 minutes; current will be ramped in
      and out for 30 seconds at the beginning and end of the 20-minute period. Subjects in the Sham
      tDCS condition will receive the same electrode placement and ramping procedures, but no
      current will be delivered between ramping.

      Linear mixed modeling will be used to assess within and between-trial exposure-relevant
      learning. Power analyses suggest that a sample of 24 (12 per condition) would adequately
      power a priori analyses when using linear mixed modeling. Mixed ANOVA will be used to assess
      recall of exposure-relevant learning. The proposed study will provide important preliminary
      data to examine the potential for medial prefrontal tDCS to augment exposure-relevant
      therapeutic learning.
    

Intervention name(s): tDCS
Intervention type(s): Device
Intervention description(s): Subjects will receive 20 minutes of multifocal transcranial direct current stimulation. The anode will be placed over the frontal pole (Fpz, 10-20 EEG) and will be surrounded by 5 return electrodes (cathodes). Current will be set at 1.5mA and will be ramped in/out at the begging and end of the 20-minutes of stimulation over the course of 30 seconds.
Other intervention name(s): transcranial direct current stimulation; transcranial electrical stimulation; Starstim®
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Double (Participant, Outcomes Assessor)
Primary purpose: Basic Science