The ventral orbito-striatal network seems to be more active during emotional processes and may be responsible for relaying the emotional OCD components such as fear and anxiety. The dorso-fronto-striatal connections are part of a system which could be responsible for mainly cognitive and executive deficits related to compulsions. Some regions of the parietal cortex, the cerebellum, and the superior temporal cortex are interconnected via the dorsolateral prefrontal cortex, meaning that there is an interface between the fronto-striatal and the fronto-parietal loop. Because of the resulting activity during symptom provocation and its functions related to attention monitoring and reaction inhibition, the parietal cortex may play a role in controlling obsessive thoughts and compulsive impulses. Therapy options for OCD are the administration of selective serotonin reuptake inhibitors and psychotherapy. To this end, both behavior therapy with exposure/response prevention and also cognitive behavior therapy have both proven effective in a number of studies. Several neuroimaging studies have shown the effects of psychotherapy on neuronal activation patterns and brain metabolism. However, the process of dynamic change itself has not yet been the object of investigation. Those few studies that have been performed by repeatedly using functional MRI in the course of psychotherapy have been conducted in dialectic-behavioral therapy applied to borderline personality disorders and in the psychodynamic therapy of chronic depression. A single-case study on patients with OCD revealed first evidence on discontinuous change of symptom severity preceded by increased dynamic complexity of therapyrelated emotions and cognitions, and a pronounced change in neuronal activity during this period. In psychotherapy research there has been a growing interest in the study of patterns of change processes. More frequently, internet-based methods have been used for process monitoring and ambulatory assessment. Meanwhile, converging findings have shown that psychotherapy is a nonlinear process with chaotic dynamics and non-stationarities, i.e., qualitative changes of dynamic patterns, reminiscent of nonequilibrium phase WY 14643 transitions of self-organizing systems. The term “phase transition” originates from physics where it indicates the spontaneous emergence of new qualities or transitions between such qualities in structures or functions of complex systems. Since there are important differences between physical and human systems, we use the term order transition. It indicates the qualitative changes of patterns in mental and behavioral systems, which are due to selforganizing processes. In complex non-equilibrium systems, they usually take place in a discontinuous way. This corresponds entirely with practical experience and empirical results on psychotherapeutic change processes, which do not occur in an incremental and linear but in a discontinuous way. Navitoclax Critical moments, the 
“kairos”, specific important experiences or insights, or spontaneous changes of symptom severity have been described repeatedly. In psychoanalysis, the Boston Change Process Study Group worked on the role of “kairos” and sudden pattern transitions in the tacit procedural knowledge of interpersonal experiences. Most prominent are findings on early rapid responses in psychotherapy which give rise to the renowned research field on sudden changes in psychotherapy. The study at hand provides evidence of discontinuous transitions in inpatient psychotherapy of OCD patients concerning their subjective experience and the corresponding neuronal activity. Such transitions could be central markers of selforganization processes.