The human brain is still not fully understood. Analysing sex differences in grey matter volume (GMV), may help explain sex-variability on the prevalence in neuropsychiatric disorders. Dis-orders such as major depression disorder (more frequent in women) and intermittent explo-sive disorder (more frequent in men) are partially characterised by emotional symptoms such as sadness or anger. Understanding whether, emotions, sex and GMV are connected in healthy adults could provide a better understanding of possible influences of emotion and sex on brain structure. The aim of this thesis was to examine the effects of sex, Anger/Hostility, and their interaction on GMV. Data from the Human Connectome Project (young adults), were analysed. We used Subsample that only contained unrelated participants (Subsample A: n=424, 228 females, 196 males, age 22-36 years). GMV was estimated from T1-weighted magnetic resonance images and was averaged over 68 cortical parcels. The influence of a confounder, the estimated total intracranial volume (eTIV), was removed from each brain re-gion using linear regression. Both raw and residuals GMV data were analysed. After testing the normality of the data (Shapiro-Wilk-Test), linear regression models with sex, Anger/Hos-tility and their interaction as predictors were performed for each brain region. Multiple com-parisons were corrected with Bonferroni. To account for a possible bias from floor values of Anger/Hostility, analyses were repeated on a second Subsample (Subsample B: n=375, 204 females, 171 males) in which subjects with the lowest value of Anger/Hostility were excluded. Sex had a significant main effect, for raw data throughout the brain cortex (67/68 regions), with higher volume in men, than in women. After accounting for the eTIV, four regions re-mained significant for main effects of sex (bilateral Insula, right Inferiorparietal, right Lateral-occipital). No significant main effect of Anger/Hostility, or its interaction with sex were found, for raw or residuals data. In Subsample B, only the main effect of sex was significant, with the same regions as Subsample A for raw data, and only one region remained significant for the main effect of sex (right Lateraloccipital) for residual data. The findings indicate widespread sex-differences in raw GMV, while a sex-related GMV difference beyond the brain size ap-peared only in four regions. Moreover Anger/Hostility showed no measurable effect on GMV, or interaction with sex on GMV, in healthy adults. This suggests that associations may only be found in a clinical group. Future studies should examine the effect of other emotional vari-ables and other brain properties.
Lynn-Sophie Spenner (Thu,) studied this question.