Transcranial Direct Current Stimulation Associated With Symptom Provocation in the Management of Patients With Treatment-Resistant Obsessive-Compulsive Disorder.

Obsessive-compulsive disorder (OCD) is a chronic and disabling condition affecting 2-3% of the population. Despite evidence-based interventions-cognitive behavioural therapy with exposure and response prevention (ERP) and serotonergic antidepressants, 40-60% of patients exhibit insufficient improvement, highlighting a substantial need for more effective therapeutic strategies.

Neuroimaging and neurophysiological studies consistently implicate dysfunction within cortico-striato-thalamo-cortical circuits, particularly the supplementary motor area (SMA) and orbitofrontal cortex (OFC). These findings have guided the development of neuromodulation interventions targeting these regions. Among them, transcranial direct current stimulation (tDCS) has emerged as a safe, accessible, and potentially effective approach for modulating aberrant neural activity in OCD.

Our research group has previously investigated a bifocal tDCS montage combining cathodal SMA stimulation with anodal right OFC stimulation. In an open-label study of 21 patients, this protocol produced clinically meaningful improvement in 15% of participants and was well tolerated. A subsequent multicentre randomised controlled trial confirmed the feasibility, safety, and potential therapeutic value of this montage, although overall effects remained modest. These findings underscore the need to optimise neuromodulatory strategies in OCD.

One promising direction is to enhance neuromodulation by manipulating the pre-stimulation neural state. Evidence suggests that the impact of tDCS depends on ongoing cortical activity, raising the possibility that activating symptom-relevant circuits immediately before stimulation could potentiate its effects. Pre-stimulation symptom provocation-also referred to as paired associative cognitive stimulation-has shown encouraging results when combined with rTMS in depression, addiction, and post-traumatic stress disorder (PTSD). In PTSD, for example, brief reactivation of traumatic memories prior to stimulation enhanced symptom reduction compared with stimulation alone.

This approach is grounded in the theory of memory, which posits that reactivated memories enter a transiently labile state during which their emotional intensity can be modified. Experimental and clinical studies have demonstrated that targeted interventions delivered during this window can weaken maladaptive emotional memories. In OCD, intrusive thoughts typically accompanied by fear, disgust, or distress may therefore constitute ideal targets for reconsolidation-based modulation.