Targeting the prefrontal-supplementary motor network in obsessive-compulsive disorder with intensified electrical stimulation in two dosages: A randomized, controlled trial

Abstract

Obsessive-Compulsive Disorder (OCD) is associated with a high disease burden, and treatment options are limited. We used intensified electrical stimulation in two dosages to target a main circuitry associated with the pathophysiology of OCD, left dorsolateral prefrontal cortex (l- DLPFC) and supplementary motor area (SMA) and assessed clinical outcomes, neuropsychological performance and brain physiology. In a double-blind, randomized-controlled trial, thirty-nine patients with OCD were randomized to sham, 2-mA or 1-mA transcranial direct current stimulation (tDCS) targeting the l-DLPFC (F3) and SMA (FC2) with anodal and cathodal stimulation respectively. The treatment included 10 sessions of 20-minute stimulation delivered twice per day with 20-min between-session intervals. Outcome measures were reduction in OCD symptoms, anxiety and depressive states, performance on a neuropsychological test battery of response inhibition, working memory, attention, and oscillatory brain activities and functional connectivity. All outcome measures except EEG were examined at pre-intervention, post- intervention and 1-month follow-up times. The 2-mA protocol significantly reduced OCD symptoms, anxiety, depression states, and improved quality of life after the intervention up to 1- month follow-up compared to the sham group, while the 1-mA protocol reduced OCD symptoms only in the follow-up and depressive state immediately after and 1-month following the intervention. Both protocols partially improved response inhibition and the 2-mA protocol reduced attention bias to OCD-related stimuli and improved reaction time in working memory performance. Both protocols increased alpha oscillatory power and the 2-mA intensified protocol decreased delta power as well. Both protocols increased connectivity in higher frequency bands at frontal-central areas compared to the sham. Modulation of the prefrontal-supplementary motor network with intensified tDCS ameliorates OCD clinical symptoms and results in beneficial cognitive effects. The 2-mA intensified stimulation resulted in larger symptom reduction and improved more converging outcome variables related to therapeutic efficacy. These results support applying the intensified prefrontal-SMA tDCS in larger trials.