title: Sex-related difference in human white matter volumes studied: Inspection of the corpus callosum and other white matter by VBM.
abstract: It has been contended that any observed difference of the corpus callosum (CC) size between men and women is not sex-related but brain-size-related. A recent report, however, showed that the midsagittal CC area was significantly larger in women in 37 brain-size-matched pairs of normal young adults. Since this constituted strong evidence of sexual dimorphism and was obtained from publicly available data in OASIS, we examined volume differences within the CC and in other white matter using voxel-based morphometry (VBM). We created a three-dimensional region of interest of the CC and measured its volume. The VBM statistics were analyzed by permutation test and threshold-free cluster enhancement (TFCE) with the significance levels at FWER < 0.05. The CC volume was significantly larger in women in the same 37 brain-size-matched pairs. We found that the CC genu was the subregion showing the most significant sex-related difference. We also found that white matter in the bilateral anterior frontal regions and the left lateral white matter near to Broca's area were larger in women, whereas there were no significant larger regions in men. Since we used brain-size-matched subjects, our results gave strong volumetric evidence of localized sexual dimorphism of white matter.
authors.affiliation: Molecular Neuroscience Research Center, Shiga University of Medical Science, Ohtsu, Shiga, Japan.
authors.forename: Akihiko
authors.initials: A
authors.lastname: Shiino
authors.affiliation: College of Information Science and Engineering, Ritsumeikan University, Kusatsu, Shiga, Japan.
authors.forename: Yen-Wei
authors.initials: YW
authors.lastname: Chen
authors.affiliation: Research Institute, Shiga Medical Center, Moriyama, Shiga, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Tanigaki
authors.affiliation: Biomedical Innovation Center, Shiga University of Medical Science, Ohtsu, Shiga, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Yamada
authors.affiliation: Molecular Neuroscience Research Center, Shiga University of Medical Science, Ohtsu, Shiga, Japan.
authors.forename: Piers
authors.initials: P
authors.lastname: Vigers
authors.affiliation: Department of Health Science, Kyoto Koka Women's University, Ukyo-ku, Kyoro, Japan.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Watanabe
authors.affiliation: Molecular Neuroscience Research Center, Shiga University of Medical Science, Ohtsu, Shiga, Japan.
authors.forename: Ikuo
authors.initials: I
authors.lastname: Tooyama
authors.affiliation: Department of Health Science, Kyoto Koka Women's University, Ukyo-ku, Kyoro, Japan.
authors.forename: Ichiro
authors.initials: I
authors.lastname: Akiguchi
mesh_terms: D003337:Corpus Callosum / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009929:Organ Size; D012727:Sex Characteristics; D012737:Sex Factors; D066127:White Matter / Q000000981:diagnostic imaging*