Cognitive and Behavioral Therapy (CBT) is recognized as a valid tool to improve Obsessive Compulsive Disorder (OCD) symptoms. The orbitofrontal cortex (OFC)-striatal circuit appears to play an important role in the pathophysiology of OCD. Neuroimaging studies suggest that CBT might change its abnormal activity in OCD patients.

The aim of this study is to use longitudinal functional Magnetic Resonance Imaging (fMRI) to assess the neural correlates of clinical improvement in OCD patients undergoing CBT.

Thirty-five OCD patients with checking compulsions undergoing 15 individual weekly CBT sessions were assessed on symptom severity with the Y-BOCS [1] at four stages of the therapies: before, during, at the end of therapy and six months later. On each assessment, patients also performed a symptom-provocation task in fMRI during which they reported their anxiety level upon watching neutral photographs, generic (validated in a population of OCD checkers) vs individualized (patient's photographs of personal objects) checking-provoking photographs.

Clinically, CBT resulted in a significant improvement (Y-BOCS scores: 24.8; 18,3; 13,7; 13.9). Behaviorally, the symptom-provocation task elicited anxiety that decreased through therapy (p < 0.05), even more so for individualized vs generic pictures (interaction p < 0.05). At the brain level, individualized pictures elicited activation in a distributed network specifically in right and left OFC, where neural response decreased during and after CBT, underlining the interest of tailoring individualized symptom-provoking items on the path to neuromarkers of response to psychotherapy.