title: Structural properties of the human corpus callosum: Multimodal assessment and sex differences.
abstract: A number of structural properties of white matter can be assessed in vivo using multimodal magnetic resonance imaging (MRI). We measured profiles of R1 and R2 relaxation rates, myelin water fraction (MWF) and diffusion tensor measures (fractional anisotropy [FA], mean diffusivity [MD]) across the mid-sagittal section of the corpus callosum in two samples of young individuals. In Part 1, we compared histology-derived axon diameter (Aboitiz et al., 1992) to MRI measures obtained in 402 young men (19.55 ± 0.84 years) recruited from the Avon Longitudinal Study on Parents and Children. In Part 2, we examined sex differences in FA, MD and magnetization transfer ratio (MTR) across the corpus callosum in 433 young (26.50 ± 0.51 years) men and women recruited from the Northern Finland Birth Cohort 1986. We found that R1, R2, and MWF follow the anterior-to-posterior profile of small-axon density. Sex differences in mean MTR were similar across the corpus callosum (males > females) while these in FA differed by the callosal segment (Body: M>F; Splenium: F>M). We suggest that the values of R1, R2 and MWF are driven by high surface area of myelin in regions with high density of "small axons".
authors.affiliation: Department of Psychiatry, University of Oulu and Oulu University Hospital, Oulu, Finland.
authors.forename: L
authors.initials: L
authors.lastname: Björnholm
authors.affiliation: Department of Radiotherapy, Oulu University Hospital, Oulu, Finland.
authors.forename: J
authors.initials: J
authors.lastname: Nikkinen
authors.affiliation: Institute of Diagnostics, Department of Diagnostic Radiology, Oulu University Hospital, Oulu, Finland.
authors.forename: V
authors.initials: V
authors.lastname: Kiviniemi
authors.affiliation: Center for Life Course Health Research, University of Oulu, Oulu, Finland.
authors.forename: T
authors.initials: T
authors.lastname: Nordström
authors.affiliation: Department of Psychiatry, University of Oulu, Oulu, Finland; Department of Psychiatry, Lapland Hospital District, Finland.
authors.forename: S
authors.initials: S
authors.lastname: Niemelä
authors.affiliation: School of Psychology, Cardiff University, Cardiff, United Kingdom.
authors.forename: M
authors.initials: M
authors.lastname: Drakesmith
authors.affiliation: School of Psychology, Cardiff University, Cardiff, United Kingdom.
authors.forename: J C
authors.initials: JC
authors.lastname: Evans
authors.affiliation: Department of Radiology, Cumming School of Medicine, University of Calgary, Calgary, Canada.
authors.forename: G B
authors.initials: GB
authors.lastname: Pike
authors.affiliation: Department of Psychiatry, University of Oulu and Oulu University Hospital, Oulu, Finland.
authors.forename: J
authors.initials: J
authors.lastname: Veijola
authors.affiliation: Rotman Research Institute, Baycrest, Toronto, Canada; Departments of Psychology and Psychiatry, University of Toronto, Toronto, Canada; Child Mind Institute, New York, USA. Electronic address: tpaus@research.baycrest.org.
authors.forename: T
authors.initials: T
authors.lastname: Paus
mesh_terms: D000293:Adolescent; D000328:Adult; D016880:Anisotropy; D003337:Corpus Callosum / Q000033:anatomy & histology* / Q000502:physiology*; D038524:Diffusion Magnetic Resonance Imaging; D056324:Diffusion Tensor Imaging; D005260:Female; D006801:Humans; D008297:Male; D012727:Sex Characteristics; D066127:White Matter / Q000033:anatomy & histology / Q000502:physiology; D055815:Young Adult