A recent study has found that people with obsessive-compulsive disorder (OCD) may have altered functioning of certain parts of the brain’s reward-based circuitry. The study, led by NARSAD Young Investigator Grantee Rachel Marsh, Ph.D., of Columbia University, used functional magnetic resonance imaging (fMRI) to look at patterns of brain activation during a reward-based learning task.

Two areas of the brain, the hippocampus and amygdala, work with parts of the frontal cortex to create our reward system—the way our brains anticipate, respond to, and learn from the things that reward us in everyday life. These areas are also involved in generating feelings of anxiety and may contribute to OCD behaviors. Evidence from earlier studies suggests that people with OCD have differences in brain circuitry in these areas, particularly when it involves spatial learning. The researchers wanted to know more about how the brains of people with OCD might differ from those without the disorder when it comes to reward-based learning tasks.

In Dr. Marsh’s study, published in September 2014 issue of The American Journal of Psychiatry, she and her colleagues asked participants navigate a virtual reality maze, finding hidden rewards. Some of the people who took part in the study had OCD, but were not taking medication. For comparison, others in the study did not have OCD.

In the “learning” phase of the challenge, participants had to use cues—things found in a natural landscape like trees and flowers—to remember which parts of the maze they had already visited (“spatial learning”). For the “control” part of the challenge, everything in the maze looked the same, but the spatial cues were scrambled so participants could not use them to find the rewards.  The fMRI data showed which areas of the brain were engaged while participants navigated the maze and received rewards in both phases of the challenge. Thus, the researchers were able to tease apart the brain’s responses to rewards with spatial learning involved, and responses to rewards when spatial learning was impossible.

Dr. Marsh and colleagues found that compared with healthy volunteers, participants with OCD had to use more brain processing resources––namely, part of the hippocampus, to learn and remember the spatial layout of the maze. In addition, OCD participants did not show activation in a brain area called the ventral striatum, an area involved in reward that was activated in non-OCD participants. The team speculates that this dysfunction might contribute to the urges to repeat a behavior characteristic of OCD.

By indicating how the brain’s reward circuitry may be altered in people with OCD, this research is part of a larger process aimed at identifying new targets that might be the basis of improved future treatments.

 

Read the abstract.