Researchers used functional MRI (fMRI) to show people who are diagnosed with obsessive-compulsive disorder (OCD) have a more difficult time learning about the safety of a stimulus compared to healthy volunteers, which may play a part in their struggles to overcome compulsive behavior.

The study, published in the Proceedings of the National Academy of Sciences, outlined researchers findings at the University of Cambridge’s Behavioural and Clinical Neuroscience Institute, where they tested 43 patients with OCD and 35 matched healthy volunteers. Researchers examined how well people with OCD were able to reverse their thinking when a previously threatening stimulus became safe and vice versa.

Volunteers were scanned using fMRI and shown one of two faces. When a participant was shown a red face, nothing happened. When shown a green face, the participant would sometimes receive a mild electric shock. The researchers were able to see if the participant learned which stimulus was safe or threatening by measuring changes in skin conductance. 

"Our study suggests that something is going wrong in the brains of people with OCD when they are learning what is safe, and this in turn affects how they perceive threats under updated circumstances," said Annemieke Apergis-Schoute, the study's first author in a statement. "This needs to be taken into consideration when we're developing future therapies to tackle the disorder. Current exposure therapies may help the patient take control over their compulsions, but our work suggests that they might never learn that their compulsions are unnecessary and they may return in times of stress."

In a related study, researchers showed that this cognitive inflexibility might be in part a result of a lack of "chatter" between specific brain areas.

"When we look at these two studies together, we can see that there is a clear imbalance between key regions at the front of the brain in people with OCD. These may underlie some of the symptoms of inflexibility that we commonly see in patients with this condition,” said Trevor Robbins, head of psychology at Cambridge and senior author on both studies.