Variation in orbitofrontal cortex volume: relation to sex, emotion regulation and affect

Abstract

Sex differences in brain structure have been examined extensively but are not completely understood, especially in relation to possible functional correlates. Our two aims in this study were to investigate sex differences in brain structure, and to investigate a possible relation between orbitofrontal cortex subregions and affective individual differences. We used tensor-based morphometry to estimate local brain volume from MPRAGE images in 117 healthy right-handed adults (58 female), age 18-40 years. We entered estimates of local brain volume as the dependent variable in a GLM, controlling for age, intelligence and whole-brain volume. Men had larger left planum temporale. Women had larger ventromedial prefrontal cortex (vmPFC), right lateral orbitofrontal (rlOFC), cerebellum, and bilateral basal ganglia and nearby white matter. vmPFC but not rlOFC volume covaried with self-reported emotion regulation strategies (reappraisal, suppression), expressivity of positive emotions (but not of negative), strength of emotional impulses, and cognitive but not somatic anxiety. vmPFC volume statistically mediated sex differences in emotion suppression. The results confirm prior reports of sex differences in orbitofrontal cortex structure, and are the first to show that normal variation in vmPFC volume is systematically related to emotion regulation and affective individual differences.

Fig. 1

Women had relatively larger local volumes in all regions shown except for planum temporale. In axial and coronal images, the left side of the brain is on the right side of the image. (A) Sex differences in the orbitofrontal cortex, coronal view, thresholded at P < 0.001, showing both the right lateral OFC (at crosshair, MNI 34, 40, –5) and ventromedial PFC (center, MNI 6, 36, –12). (B) Sex differences in right WM, near basal ganglia, P < 0.0001, MNI 28, −21, 8. (C) Sex differences in the left basal ganglia and WM, P < 0.0001, MNI −26, −7, 21. (D) Sex differences in the cerebellum, P < 0.0001, MNI 5, −44, −8. (E) Sex differences in the left planum temporale (at crosshair), P < 0.001, MNI −52, −17, 14.