Gray-white matter contrast as an index of neurobiological alterations in anorexia nervosa

This neuroimaging study sought to characterize differences in cortical gray-white matter contrast (GWC) between individuals with anorexia nervosa (AN) and age-matched healthy controls (HC) and compare these findings with conventional cortical thickness (CT) measures. The study included 58 female participants (29 AN, 29 HC). T1-weighted images were acquired using a 3 T scanner and processed with FreeSurfer. GWC maps were calculated at each cortical vertex. Vertex-wise general linear models assessed group differences in GWC controlling for age only, and controlling for age and vertex-wise CT. A separate model tested CT differences. Models were corrected for multiple comparisons using cluster-wise correction. Spearman correlations related mean GWC in significant clusters to BMI at scan, age at onset, and illness duration. The age-only model revealed two clusters in the left hemisphere with higher GWC in patients with AN, namely the inferior temporal cortex and medial orbitofrontal cortex. No clusters survived in the model controlling for age and CT. The CT analysis revealed no significant group differences. Mean GWC in clusters did not correlate with clinical severity indices in AN. Patients with AN exhibit focal increases in GWC despite the absence of detectable cortical thinning, suggesting that the GWC can provide complementary information in understanding the neurobiology of AN. The elimination of GWC differences when adjusting for CT likely reflects shared variance rather than true absence of effect. Lack of correlations with clinical indices may be due to limited sample size. Future longitudinal and multimodal studies are warranted to determine the underpinnings of GWC alterations.