title: Early postnatal development of corpus callosum and corticospinal white matter assessed with quantitative tractography.
abstract: OBJECTIVE
  The early postnatal period is perhaps the most dynamic phase of white matter development. We hypothesized that the early postnatal development of the corpus callosum and corticospinal tracts could be studied in unsedated healthy neonates by using novel approaches to diffusion tensor imaging (DTI) and quantitative tractography.
  
  
  METHODS
  Isotropic 2 x 2 x 2 mm(3) DTI and structural images were acquired from 47 healthy neonates. DTI and structural images were coregistered and fractional anisotropy (FA), mean diffusivity (MD), and normalized T1-weighted (T1W) and T2-weighted (T2W) signal intensities were determined in central midline and peripheral cortical regions of the white matter tracts of the genu and splenium of the corpus callosum and the central midbrain and peripheral cortical regions of the corticospinal tracts by using quantitative tractography.
  
  
  RESULTS
  We observed that central regions exhibited lower MD, higher FA values, higher T1W intensity, and lower T2W intensity than peripheral cortical regions. As expected, MD decreased, FA increased, and T2W signal intensity decreased with increasing age in the genu and corticospinal tract, whereas there was no significant change in T1W signal intensity. The central midline region of the splenium fiber tract has a unique pattern, with no change in MD, FA, or T2W signal intensity with age, suggesting different growth trajectory compared with the other tracts. FA seems to be more dependent on tract organization, whereas MD seems to be more sensitive to myelination.
  
  
  CONCLUSIONS
  Our novel approach may detect small regional differences and age-related changes in the corpus callosum and corticospinal white matter tracts in unsedated healthy neonates and may be used for future studies of pediatric brain disorders that affect developing white matter.
authors.affiliation: Schizophrenia Research Center and Department of Psychiatry, University of North Carolina, Chapel Hill, NC 27599-7160, USA. jgilmore@med.unc.edu
authors.forename: J H
authors.initials: JH
authors.lastname: Gilmore
authors.forename: W
authors.initials: W
authors.lastname: Lin
authors.forename: I
authors.initials: I
authors.lastname: Corouge
authors.forename: Y S K
authors.initials: YS
authors.lastname: Vetsa
authors.forename: J K
authors.initials: JK
authors.lastname: Smith
authors.forename: C
authors.initials: C
authors.lastname: Kang
authors.forename: H
authors.initials: H
authors.lastname: Gu
authors.forename: R M
authors.initials: RM
authors.lastname: Hamer
authors.forename: J A
authors.initials: JA
authors.lastname: Lieberman
authors.forename: G
authors.initials: G
authors.lastname: Gerig
mesh_terms: D003337:Corpus Callosum / Q000033:anatomy & histology* / Q000254:growth & development*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D007231:Infant, Newborn; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D009413:Nerve Fibers, Myelinated / Q000502:physiology* / Q000648:ultrastructure*; D011712:Pyramidal Tracts / Q000033:anatomy & histology* / Q000254:growth & development*