White matter sexual dimorphism of the adult human brain

Abstract

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.

Adolescent maturation of the prefrontal cortex: Role of stress and sex in shaping adult risk for compromise

“…Although in the human literature there exist no consensus as to the presence of a sexual dimorphism in either the brain's structure or white matter development, 30,87 in the subset of studies that include both male and female subjects, we see a clear sex difference. From this, it is critical that future studies include both male and female subjects in their design.…”

“…Conversely, a separate study found evidence that females have regionspecific elevations in myelin in the corpus callosum in the genu vs splenium vs main body 86. Females display increased volume in the hippocampus, locus coeruleus, Broca's area and Wernicke's areas when compared to their male counterparts 33,87,88. In humans, these sex specific asymmetries are found in multiple brain regions16,40,89 that are not reflected in global white matter assessments87 and not due to a sexspecific difference in overall brain volume 88.…”

“…Females display increased volume in the hippocampus, locus coeruleus, Broca's area and Wernicke's areas when compared to their male counterparts 33,87,88. In humans, these sex specific asymmetries are found in multiple brain regions16,40,89 that are not reflected in global white matter assessments87 and not due to a sexspecific difference in overall brain volume 88. These changes co-occur with differences in behavior, with female subjects on average presenting increased pro-social behaviors, whereas male subjects exhibit increased spatial and motor abilities, seen in both rodent models and human studies 18,33,47,79,87.…”

“…In humans, these sex specific asymmetries are found in multiple brain regions16,40,89 that are not reflected in global white matter assessments87 and not due to a sexspecific difference in overall brain volume 88. These changes co-occur with differences in behavior, with female subjects on average presenting increased pro-social behaviors, whereas male subjects exhibit increased spatial and motor abilities, seen in both rodent models and human studies 18,33,47,79,87. Sex hormones influence both the development and lifelong plasticity of white matter in the brain [90][91][92].…”

Combined Use of MRI, fMRIand Cognitive Data for Alzheimer’s Disease: Preliminary Results

“…These masks were employed to quantify ROI volume and connectivity as in [54,55]. The whole brain, intracranial, and ROIs volume were determined with the get_totals script (cs.ucl.ac.uk), such as in [57,58]. This script takes one segmented MRI set, i.e., all the images for a given brain tissue, as input and then returns its volume expressed in mm 3 .…”