Both people with obsessive-compulsive disorder (OCD) and their unaffected family members show decreased activity in a brain region that's key to decision-making, and researchers say the finding could help them identify people who are at risk of developing the disorder. In a new study, volunteers performed a task that required mental flexibility, as the correct response changed over time. Researchers used a functional MRI to take brain scans during the experiment, and found that people with OCD and their relatives showed decreased activity in the orbitofrontal cortex.