Abnormalities in deep-brain morphology and orbitofrontal cortical thinning relate to reward processing and body mass...

Research examining the neural correlates of obesity has recently expanded. However, limited attention has focused on identifying unique brain signatures associated with obesity, particularly in adolescents. The aim of this study was to use surface-based approaches to examine the integrity of brain structures involved in processing the pleasurable effects of food with body mass and food reward sensitivity in adolescent girls.

Structural morphology of the nucleus accumbens, amygdala, pallidum, and orbitofrontal cortex was examined in 89 adolescent girls with body mass ranging from normal to obese. High-resolution T1-weighted MPRAGE images were used to characterize deep-brain nuclei with high-dimensional diffeomorphic mapping procedures, while cortical thickness was derived from the FreeSurfer toolkit.

Results revealed that zBMI was significantly associated with the shape of the left amygdala (β = -1.1, p < 0.021, 95% CI = -2.02, -0.16), volume of the right and left pallidum (β = 49.66, p < 0.010, 95% CI = 11.74, 87.58; β = 47.87, p < 0.017, 95% CI = 8.48, 87.25), and cortical thickness of the lateral and right medial orbitofrontal cortex (β = -0.06, p < 0.001, 95% CI = -0.09, -0.04; β = -0.05, p = 0.004, 95% CI = -0.08, -0.02). Sensitivity to food reward significantly predicted volume of the right nucleus accumbens (β = 0.66, p = 0.047, 95% CI = 0.01, 1). Contrast mapping for surface shape of the amygdala revealed significant outward deformation of the posterior lateral left amygdala and an inward deformation of the basolateral left amygdala in the group with overweight/obesity.

Integrity of the left amygdala and orbitofrontal cortex varies as a function of body mass, with greater localized amygdalar volume loss, pallidum volume, and increased cortical thinning of the orbitofrontal cortex occurring as weight increases. Thus, overweight/obesity may be associated with surface-based abnormalities in brain structures associated with processing of reward value related to food. Overall, findings highlight the importance of understanding changes in reward-related brain regions and how they pertain to variability in body mass in adolescent girls.