Article

Men and women are different: diffusion tensor imaging reveals sexual dimorphism in the microstructure of the thalamus, corpus callosum and cingulum.

Philipps-University Marburg, Center of Brain Imaging, Department of Neurology, Marburg, Germany.
NeuroImage (impact factor: 5.89). 11/2010; 54(4):2557-62. DOI:10.1016/j.neuroimage.2010.11.029 pp.2557-62
Source: PubMed

ABSTRACT Numerous magnetic resonance imaging (MRI) studies have addressed the question of morphological differences of the brain of men and women, reporting conflicting results regarding brain size and the ratio of gray and white matter. In the present study, we used diffusion tensor imaging (DTI) to delineate sex differences of brain white matter.
We investigated brain microstructure in 25 male and 25 female healthy subjects using a 3T MRI scanner. Whole-head DTI scans were analyzed without a-priori hypothesis using Tract-Based Spatial Statistics (TBSS) calculating maps of fractional anisotropy (FA), radial diffusivity (RD, a potential marker of glial alteration and changes in myelination) and axial diffusivity (AD, a potential marker of axonal changes).
DTI revealed regional microstructural differences between the brains of male and female subjects. Those were prominent in the thalamus, corpus callosum and cingulum. Men showed significantly (p<0.0001) higher values of fractional anisotropy and lower radial diffusivity in these areas, suggesting that the observed differences are mainly due to differences in myelination.
As a novel finding we showed widespread differences in thalamic microstructure that have not been described previously. Additionally, the present study confirmed earlier DTI studies focusing on sexual dimorphism in the corpus callosum and cingulum. All changes appear to be based on differences in myelination. The sex differences in thalamic microstructure call for further studies on the underlying cause and the behavioral correlates of this sexual dimorphism. Future DTI group studies may carefully control for gender to avoid confounding.

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Keywords

25 female healthy subjects
 
3T MRI scanner
 
a-priori hypothesis
 
axial diffusivity
 
brain microstructure
 
brain size
 
brain white matter
 
conflicting results
 
corpus callosum
 
delineate sex differences
 
diffusion tensor imaging
 
Future DTI group studies
 
lower radial diffusivity
 
Numerous magnetic resonance imaging
 
radial diffusivity
 
regional microstructural differences
 
thalamic microstructure
 
thalamic microstructure call
 
Whole-head DTI scans
 
women