To better understand its neurobiology, Feusner and colleagues examined 17 patients with BDD and matched them by sex, age and education level with 16 healthy people. Participants underwent functional magnetic resonance imaging (fMRI) while viewing photographs of two faces — their own and that of a familiar actor — first unaltered, and then altered in two ways to parse out different elements of visual processing.

One altered version included only high-spatial frequency information, which would allow detailed analysis of facial traits, including blemishes and hairs. The other showed only low-spatial frequency information, conveying the general shape of the face and the relationship between facial features.

Compared to the control participants, individuals with BDD demonstrated abnormal brain activity in visual processing systems when viewing the unaltered and low-spatial frequency versions of their own faces. They also had unusual activation patterns in their frontostriatal systems, which help control and guide behavior and maintain emotional flexibility in responding to situations.

Brain activity in both systems correlated with the severity of symptoms. In addition, differences in activity in the frontostriatal system varied based on participant reports of how disgusting or repulsive they found each image. Basically, how ugly the individuals viewed themselves appeared to explain abnormal brain activity in these systems.

The abnormal activation patterns, especially in response to low-frequency images, suggest that individuals with body dysmorphic disorder have difficulties perceiving or processing general information about faces.

“This may account for their inability to see the big picture — their face as a whole,” Feusner said. “They become obsessed with detail and think everybody will notice any slight imperfection on their face. They just don’t see their face holistically.”