A meta-analysis of sex differences in human brain structure

Abstract

HighlightsThis is the first meta-analysis of sex differences in the typical human brain.Regional sex differences overlap with areas implicated in psychiatric conditions.The amygdala, hippocampus, planum temporale and insula display sex differences.On average, males have larger brain volumes than females.Most articles providing sex differences in volume are in the ‘mature’ category.

Asymmetry within and around the human planum temporale is sexually dimorphic and influenced by genes involved in steroid hormone receptor activity

“…We found that the PT as defined by the HO atlas showed the strongest sexually dimorphic asymmetry of any cortical region, which remained significant when adjusted conservatively for multiple testing over all cortical regions. Males showed stronger leftward PT regional lateralisation than females, which was consistent with some of the larger, previous studies where a sex difference has been reported (de Courten-Myers, 1999;Good et al, 2001;Shapleske et al, 1999; see also a recent study by Ruigrok et al (2014) showing females to have larger volumes of the right PT than males). The same sexual dimorphism in PT AI that we observed in BIG was also found in the two SHIP datasets, comprised primarily of older adults from north Germany, which totalled 1823 subjects.…”

Circulating androgens correlate with resting-state MRI in transgender men

“…In the present study, natal men relative to natal women and transgender men differed in resting-state measures in IFG thus being consistent with this prior work. Moreover, resting-state activity between men and women also differed in the left precentral gyrus (BA6), an area that has been found larger in men than in women (Ruigrok et al, 2014). Interestingly, whereas resting activity of the IFG differed between transgender men and their gender identity, in the precentral gyrus, transgender men differed from natal women in LFF, an effect that was supported by positive correlations with androgens in this structure.…”

“…Sexual dimorphism in the frontal cortex has been observed in a variety of settings. For example, inferior frontal gyrus volume (IFG, BA44/45) is modulated by the androgen receptor (AR) gene in women (Raznahan et al, 2010), IFG is larger in women than in men (Ruigrok et al, 2014), and is an area that displays sex differences in activation patterns in prefrontally-mediated tasks such as verbal fluency (Gauthier et al, 2009). In the present study, natal men relative to natal women and transgender men differed in resting-state measures in IFG thus being consistent with this prior work.…”

“…Additionally, although the present study utilized state-of-the-art hormonal analyses providing great sensitivity with regards to hormonal assays, hormonal levels in the blood may not necessarily reflect hormonal levels in the brain. Given these limitations, the data are best seen in a larger context of converging studies examining the impact of sex hormones on brain structure and function beyond those of transgender persons such as endocrine conditions (Lentini et al, 2012;Merke et al, 2003;Mueller et al, 2009;Mueller et al, 2011;Skakkebaek et al, 2014) or general sex differences (Raznahan et al, 2010;Ruigrok et al, 2014). Finally, while much prior MRI work has invested effort to exclude transgender persons with psychiatric comorbidity, we decided to include all participants based on the notion that such a sample is more representative given a 70% prevalence rate of a current or lifetime psychiatric diagnosis in a large pan-European sample of individuals with gender dysphoria (Heylens et al, 2014).…”

Le syndrome d’insensibilité aux androgènes et activité cérébrale chez la femme

“…> Dans l'espèce humaine, des différences entre sexes ont été observées à différents niveaux : les capacités cognitives [1], la structure du cerveau [2] et l'activité cérébrale associée à l'exécution de tâches cognitives ou émotionnelles [3]. Cependant, les mécanismes exacts impliqués dans la différenciation sexuelle du cerveau et du comportement chez l'homme sont encore fortement discutés.…”