Imaging the development of sex differences in the brain

Sex differences are pervasive in the brain and affect many behaviours and disorders, such as psychiatric disorders. However, current studies investigating sex differences in neuroanatomy are primarily cross- sectional, focal examinations. This thesis aims to study sex differences in the whole brain, as they develop, beginning in early life. Male and female C57BL/6 mice were longitudinally scanned at nine time points with in vivo manganese enhanced magnetic resonance imaging. An investigation of the three canonical sex differences in the brain reveal different developmental trajectories amongst areas. Next, a linear mixed effects model centred at each time point revealed widespread patterns of larger areas in males predominating in early life, while larger areas in females predominate in post-pubertal life. Finally, k-means clustering of sexually dimorphic development across life reveals an area in the cortex larger in females, and the coordinated growth of a sexually dimorphic network of structures related to vomeronasal circuitry.%%%%M.Sc.