White Matter Sexual Dimorphism of the Adult Human Brain.

Sex-biased psychophysiology, behavior, brain function, and conditions are extensive, yet underlying structural brain mechanisms remain unclear. There is contradicting evidence regarding sexual dimorphism when it comes to brain structure, and there is still no consensus on whether or not there exists such a dimorphism for brain white matter. Therefore, we conducted a voxel-based morphometry (VBM) analysis along with global volume analysis for white matter across sex. We analyzed 384 T1-weighted MRI brain images (192 male, 192 female) to investigate any differences in white matter (WM) between males and females. In the VBM analysis, we found males to have larger WM, compared to females, in occipital, temporal, insular, parietal, and frontal brain regions. In contrast, females showed only one WM region to be significantly larger than males: the right postcentral gyrus in the parietal lobe region. Although, on average, males showed larger global WM volume, we did not find any significant difference in global WM volume between males and females.

A voxel-based morphometric magnetic resonance imaging study of the brain detects age-related gray matter volume changes in healthy subjects of 21-45 years old.

Previous and more recent work of analyzing structural changes in the brain suggest that certain brain regions such as the frontal lobe are among the brain regions profoundly affected by the aging process across males and females. Also, a unified model of structural changes in a normally aging brain is still lacking. The present study investigated age-related structural brain changes in gray matter from young to early middle-age adulthood for males and females. Magnetic resonance images of 215 normal and healthy participants between the ages of 21-45 years were acquired. Changes in gray matter were assessed using voxel-based morphometry and gray matter volumetric analysis. The results showed significant decrease in gray matter volume between the youngest and oldest groups in the following brain regions: frontal, temporal, and parietal lobes. Grey matter loss in the frontal lobe was among the most widespread of all brain regions across the comparison groups that showed significant age-related changes in grey matter for both males and females. This work provides a unique pattern of age-related decline of normal and healthy adult males and females that can aid in the future development of a unified model of normal brain aging.