Review: magnetic resonance imaging of male/female differences in human adolescent brain anatomy

TLDR

Neuroimaging advances have produced extensive data on male/female brain differences, showing a ~10 % larger total brain size in males and sex‑specific variations in structures such as the caudate, amygdala, hippocampus, cerebellum, and cortical gray matter, which are influenced by hormones and genetics. The review aims to synthesize adolescent MRI studies on male/female brain differences. The reported differences depend on acquisition and analysis methods, adjustment for total brain volume, and participant age. Longitudinal data reveal that cortical gray matter peaks earlier in females, while white matter expands more rapidly in adolescent males, widening sex differences over development.

Abstract

Improvements in neuroimaging technologies, and greater access to their use, have generated a plethora of data regarding male/female differences in the developing brain. Examination of these differences may shed light on the pathophysiology of the many illnesses that differ between the sexes and ultimately lead to more effective interventions. In this review, we attempt to synthesize the anatomic magnetic resonance imaging (MRI) literature of male/female brain differences with emphasis on studies encompassing adolescence – a time of divergence in physical and behavioral characteristics. Across all ages total brain size is consistently reported to be about 10% larger in males. Structures commonly reported to be different between sexes include the caudate nucleus, amygdala, hippocampus, and cerebellum – all noted to have a relatively high density of sex steroid receptors. The direction and magnitude of reported brain differences depends on the methodology of data acquisition and analysis, whether and how the subcomponents are adjusted for the total brain volume difference, and the age of the participants in the studies. Longitudinal studies indicate regional cortical gray matter volumes follow inverted U shaped developmental trajectories with peak size occurring one to three years earlier in females. Cortical gray matter differences are modulated by androgen receptor genotyope and by circulating levels of hormones. White matter volumes increase throughout childhood and adolescence in both sexes but more rapidly in adolescent males resulting in an expanding magnitude of sex differences from childhood to adulthood.