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

强迫症（OCD）是一种以强迫和强迫为特征的精神疾病。强迫症被描述为反复出现和持续的想法或冲动，患者认为这些想法或冲动是不必要的，侵入性的，难以抑制的。强迫行为被定义为患者无法抑制的重复性行为或心理想法。因此，抑制缺陷被认为是强迫症的核心精神病理机制。强迫症的抑制缺陷已被证明与主要在外侧和内侧额叶区、纹状体和丘脑的激活减少有关，并可能与特定静息状态网络（即额顶叶网络、突出网络）的低连通性有关。越来越多的证据表明，经颅直流电刺激（tDCS）可以改善健康受试者的抑制表现，但迄今为止还没有对强迫症患者进行类似的研究。在此背景下，计划的项目旨在调查阳极tDCS对一组强迫症患者（n=44）的临床症状、行为抑制及其神经相关因素的影响。我们期望preSMA tDCS刺激与强制性冲动和行为抑制的改善同时发生。此外，这种抑制能力的提高与主要额叶区域的激活增加、受刺激区域的功能连通性增加以及精神病理相关网络（即额顶叶网络、显著性网络）的静息状态功能连通性增加有关。与tDCS相关的行为抑制和临床状态的改善将强调抑制能力的临床相关性，并证明tDCS对强迫症的治疗效果。此外，tDCS增强的激活和连通性将揭示行为抑制相关改善的神经生物学机制，并证明其改变的精神病理学相关性。

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.