Effects of transcranial direct current stimulation (tDCS) on response inhibition and neuronal activity in obsessive-compulsive disorder

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Obsessive-compulsive disorder (OCD) is a psychiatric disease characterized by obsessions and compulsions. Obsessions are described as recurrent and persistent thoughts or impulses which are perceived by the patients as unwanted, intrusive and hard to inhibit. Compulsions are defined as repetitive behaviours or mental thoughts which patients are unable to inhibit. Hence, a deficit in inhibition is considered as a core psychopathological mechanisms of OCD. Inhibition deficits in OCD have been shown to go along with decreased activation in mainly lateral and medial frontal regions, striatum, and thalamus and might be associated with hypoconnectivities in specific resting-state networks (i.e., frontoparietal network, salience network). There is mounting evidence indicating that transcranial direct current stimulation (tDCS) improves inhibition performance in healthy subjects but no comparable studies have been performed in patients with OCD up to now. Against this background the planned project aims at investigating the effects of anodal tDCS on clinical symptoms, behavioral inhibition and its neural correlates in a group of patients suffering from OCD (n=44). We expect preSMA tDCS stimulation to go along with an improvement in compulsory impulses and behavioral inhibition. This improved inhibition capability is moreover expected to go along with increased activation in mainly frontal regions, an increase in functional connectivity of the stimulated region as well as an increase in resting-state functional connectivity in psychopathologically relevant networks (i.e., frontoparietal network, salience network). A tDCS-related improvement in behavioral inhibition and clinical state would underline the clinical relevance of inhibitory capacities and demonstrate the therapeutic efficacy of tDCS for OCD. Moreover, enhanced activation and connectivity as a result of tDCS would reveal the neurobiological mechanisms underlying the associated improvements in behavioral inhibition and demonstrate the psychopathological relevance of their alterations.