Sex differences in brain anatomy

Over the past decades scientific studies have revealed a number of striking sex differences in the human brain. This chapter highlights some of the most important discoveries with particular emphasis on macro-anatomical observations based on magnetic resonance imaging (MRI) data. Cross-references to animal studies and to post mortem analyses, as well as an overview with respect to micro-anatomical findings, are provided. The chapter concludes with a discussion of possible determinants of sex differences in brain anatomy. The main goal of this chapter is to exemplify the variety of findings and to demonstrate how the presence, magnitude, and direction of observed sex differences strongly depend on a number of factors including (but not limited to) the following: the brain structure examined (cerebral cortex, corpus callosum, etc.), the specific brain feature assessed (cortical thickness, cortical convolution, etc.), the degree of regional specificity (global gray matter volume, voxel-wise gray matter volume, etc.), and whether measurements are adjusted for individual brain size or not.