title: Development and aging of the healthy human brain uncinate fasciculus across the lifespan using diffusion tensor tractography.
abstract: The human brain uncinate fasciculus (UF) is an important cortico-cortical white matter pathway that directly connects the frontal and temporal lobes, although there is a lack of conclusive support for its exact functional role. Using diffusion tensor tractography, we extracted the UF, calculated its volume and normalized it with respect to each subject's intracranial volume (ICV) and analyzed its corresponding DTI metrics bilaterally on a cohort of 108 right-handed children and adults aged 7-68 years. Results showed inverted U-shaped curves for fractional anisotropy (FA) with advancing age and U-shaped curves for radial and axial diffusivities reflecting white matter progressive and regressive myelination and coherence dynamics that continue into young adulthood. The mean FA values of the UF were significantly larger on the left side in children (p=0.05), adults (p=0.0012) and the entire sample (p=0.0002). The FA leftward asymmetry (Left>Right) is shown to be due to increased leftward asymmetry in the axial diffusivity (p<0.0001) and a lack of asymmetry (p>0.23) for the radial diffusivity. This is the first study to provide baseline normative macro and microstructural age trajectories of the human UF across the lifespan. Results of this study may lend themselves to better understanding of UF role in future behavioral and clinical studies.
authors.affiliation: Department of Diagnostic and Interventional Imaging, University of Texas Medical School at Houston, 6431 Fannin Street, MSB 2.100, Houston, TX 77030, USA. Khader.M.Hasan@uth.tmc.edu
authors.forename: Khader M
authors.initials: KM
authors.lastname: Hasan
authors.forename: Amal
authors.initials: A
authors.lastname: Iftikhar
authors.forename: Arash
authors.initials: A
authors.lastname: Kamali
authors.forename: Larry A
authors.initials: LA
authors.lastname: Kramer
authors.forename: Manzar
authors.initials: M
authors.lastname: Ashtari
authors.forename: Paul T
authors.initials: PT
authors.lastname: Cirino
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Papanicolaou
authors.forename: Jack M
authors.initials: JM
authors.lastname: Fletcher
authors.forename: Linda
authors.initials: L
authors.lastname: Ewing-Cobbs
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000375:Aging; D002648:Child; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D005625:Frontal Lobe / Q000033:anatomy & histology / Q000254:growth & development*; D007839:Functional Laterality; D006803:Human Development; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D009434:Neural Pathways / Q000033:anatomy & histology / Q000254:growth & development; D012727:Sex Characteristics; D013702:Temporal Lobe / Q000033:anatomy & histology / Q000254:growth & development*; D055815:Young Adult