Sex Differences in the Adult Human Brain: Evidence from 5216 UK Biobank Participants

Abstract

Sex differences in the human brain are of interest for many reasons: for example, there are sex differences in the observed prevalence of psychiatric disorders and in some psychological traits that brain differences might help to explain. We report the largest single-sample study of structural and functional sex differences in the human brain (2750 female, 2466 male participants; mean age 61.7 years, range 44–77 years). Males had higher raw volumes, raw surface areas, and white matter fractional anisotropy; females had higher raw cortical thickness and higher white matter tract complexity. There was considerable distributional overlap between the sexes. Subregional differences were not fully attributable to differences in total volume, total surface area, mean cortical thickness, or height. There was generally greater male variance across the raw structural measures. Functional connectome organization showed stronger connectivity for males in unimodal sensorimotor cortices, and stronger connectivity for females in the default mode network. This large-scale study provides a foundation for attempts to understand the causes and consequences of sex differences in adult brain structure and function.

Multimodal fusion of structural and functional brain imaging in depression using linked independent component analysis

“…Men had larger global brain volume and surface area than women (IC1), which is consistent with previous studies (e.g., Ritchie et al, 2018). Additionally, women had higher subject weights in IC13, reflecting lower FA in the corticospinal tract, portions of the superior longitudinal fasciculi and posterior thalamic radiation compared to men, generally in line with a large-scale UK Biobank study (Ritchie et al, 2018). We also found that men had greater DMN amplitude (IC5) than women, which adds to previous inconclusive findings (Mowinckel et al, 2012;Weissman-Fogel, Moayedi, Taylor, Pope, & Davis, 2010) and contrasts a previous report suggesting effects in the opposite direction (Jamadar et al, 2018).…”

“…Men had larger global brain volume and surface area than women (IC1), which is consistent with previous studies (e.g., Ritchie et al, ). Additionally, women had higher subject weights in IC13, reflecting lower FA in the corticospinal tract, portions of the superior longitudinal fasciculi and posterior thalamic radiation compared to men, generally in line with a large‐scale UK Biobank study (Ritchie et al, ).…”

Enhancement of indirect functional connections with shortest path length in the adult autistic brain

“…While sex differences are well established for measures of restingstate functional connectivity in TD individuals (Biswal et al, 2010;Ritchie et al, 2018), these differences are currently poorly understood in autism partly due to the limited number of autistic females participating in neuroimaging studies. The question arises whether the brain functional organization differs between autistic males and females after taking typical sex differences into account.…”

Age but no sex effects on subareas of the amygdala

“…Consequently, raw (sub)volumes of the amygdala were larger in men than in women by up to 11%. The third study contained more than 5,000 subjects (Ritchie et al, 2018) and revealed that, although men had a larger amygdala than women, the effect was only small (d = 0.18, bilaterally). Depicted are the area-specific trajectories (i.e., after removing the variance associated with sex and TIV) for the amygdala as a whole (AMG), as well as the centromedian (CM), laterobasal (LB), and superficial (SF) subareas were applied, sex differences were only small and not significant.…”