title: Asymmetry, sex differences and age-related changes in the white matter in the healthy elderly: a tract-based study.
abstract: BACKGROUND
  Hemispherical asymmetry, sex differences and age-related changes have been reported for the human brain. Meanwhile it was still unclear the presence of the asymmetry or sex differences in the human brain occurred whether as a normal development or as consequences of any pathological changes. The aim of this study was to investigate hemispherical asymmetry, sex differences and age-related changes by using a tract-based analysis in the nerve bundles.
  
  
  METHODS
  40 healthy elderly subjects underwent magnetic resonance diffusion tensor imaging, and we calculated fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values along the major white matter bundles.
  
  
  RESULTS
  We identified hemispherical asymmetry in the ADC values for the cingulate fasciculus in the total subject set and in males, and a sex difference in the FA values for the right uncinate fasciculus. For age-related changes, we demonstrated a significant increase in ADC values with advancing age in the right cingulum, left temporal white matter, and a significant decrease in FA values in the right superior longitudinal fasciculus.
  
  
  CONCLUSIONS
  In this study, we found hemispherical asymmetry, sex differences and age-related changes in particular regions of the white matter in the healthy elderly. Our results suggest considering these differences can be important in imaging studies.
authors.affiliation: Department of Psychiatry, Nara Medical University, Kashihara, Japan. kitaso@naramed-u.ac.jp.
authors.forename: Soichiro
authors.initials: S
authors.lastname: Kitamura
authors.forename: Masayuki
authors.initials: M
authors.lastname: Morikawa
authors.forename: Kuniaki
authors.initials: K
authors.lastname: Kiuchi
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Taoka
authors.forename: Masami
authors.initials: M
authors.lastname: Fukusumi
authors.forename: Kimihiko
authors.initials: K
authors.lastname: Kichikawa
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Kishimoto