Neuroimaging and modulation of the decision-making mechanisms of compulsivity in obsessive-compulsive disorder 

By applying and integrating concepts and methods from behavioral modeling and model-based fMRI, we aim to examine how aberrancies in the utilization of learning-based decision-making strategies can lead to compulsive behaviors in OCD at the behavioral and neural levels. Furthermore, we aim to test how the underlying circuit mechanisms of those decision-making strategies can be modulated by using noninvasive brain stimulation methods such as tDCS and TMS. We specifically focus on an arbitration mechanism that functions dynamically to assess the reliability of the involved decision-making strategies with the subsequent allocation of behavior control to the more reliable one.   

Computational psychiatry of decision-making

Our group is involved in two NIMH-funded projects led by Caltech decision neuroscientist, John O’Doherty. In one project, a computational assessment battery consisting of four distinct yet interrelated decision-making tasks including gain/loss learning, model-based vs model-free learning, exploration/exploitation, and social learning is utilized to quantify individual differences across a range of computational mechanisms relevant to the diagnosis and treatment of psychiatric disorders with focus on obsessive-compulsive spectrum, depressive and anxiety disorders. In another project, the aim is to comprehensively investigate the relationship between the psychological constructs of goal-directed and habitual control and their proposed computational bases of model-based and model-free reinforcement learning in humans at both behavioral and neural levels by using and integrating behavioral modeling and neuroimaging (resting-state and task-based fMRI and diffusion weighted imaging) techniques.

 Neuroimaging of reward processing and decision-making in anorexia nervosa

In this line of research, we are exploring the circuit mechanisms of reward processing (both wanting/motivational and liking aspects) and decision-making in anorexia nervosa by using resting-state and task-based fMRI and diffusion weighted imaging. Our research showed that in patients with anorexia, ritual (compulsive) behaviors are associated with white matter tracts structural changes in the habitual decision-making circuit suggesting a new potential target for the treatment of very difficult-to-treat ritual (compulsive) behaviors in anorexia (Tadayonnejad et al., 2021).

Neuroimaging and transcranial magnetic stimulation (TMS) treatment of OCD with comorbid depression

OCD with comorbid depression (OCD-MDD) is a complex psychiatric condition associated with increased anxiety and disability, heightened obsessive-compulsive symptom severity, and poorer response to available treatment options. In this more clinically oriented line of research, we aim to obtain a better understanding of the underlying circuit mechanisms of OCD-MDD and develop more effective circuit-based brain stimulation treatments. By examining the implicated circuits in OCD-MDD, we found that in this complicated psychiatric condition both within and between circuit dynamics are implicated (Tadayonnejad et al., 2018). Furthermore, we recently developed a new TMS protocol for the treatment of OCD-MDD and got promising results for alleviating both OCD and depressive symptoms (Tadayonnejad et al., 2020).