The Brain Correlates of Personality and Sex Differences

Personality neuroscience is a rapidly expanding field of study fueled by a growing interest in understanding the structural brain correlates of individual differences in personality. Data on the structural brain correlates of personality are especially lacking from large-scale studies, and are nearly nonexistent in the adolescent age group. Furthermore, the role of sex differences in structural brain changes associated with personality are rarely considered. To address this gap in knowledge, this thesis investigates the structural brain correlates of personality and sex differences in structure at age fourteen. A large sample of adolescents (N = 2000) were drawn from the IMAGEN project. Data on adolescents’ puberty status, IQ, and personality were collected through adolescent-reported questionnaires and interviews. The structural brain correlates of personality were examined utilizing personality variables from the NEO Five Factor Inventory (NEO-FFI) and Voxel-Based Morphometry (VBM). Our results showed few correlations between any dimension of the NEO-FFI and regional grey matter volume (GMV). In the total sample, a negative correlation was found for agreeableness and bilateral supplementary motor area (SMA), which was also present in the male subsample. The female sample showed a significant negative correlation between extraversion and the right SMA, and a positive correlation in the left cerebellum. A nonlinear effect of extraversion positively correlated with the right precuneus in females. The present study suggests personality traits are not strongly reflected in GMV during adolescence. This thesis includes a discussion on future directions and suggestions for assessing the brain correlates of personality.