Early childhood development of white matter fiber density and morphology
Dennis Dimond,
Christiane S. Rohr,
Robert E. Smith,
Thijs Dhollander,
Ivy Cho,
Catherine Lebel,
Deborah Dewey,
Alan Connelly,
Signe Bray
Affiliations
Dennis Dimond
Department of Neuroscience, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada; Alberta Children’s Hospital Research Institute, University of Calgary, Calgary, AB, Canada; Child and Adolescent Imaging Research Program, University of Calgary, Calgary, AB, Canada; Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada; Corresponding author. Alberta Children’s Hospital, 28 Oki Drive NW, Calgary, Alberta, T3B 6A8, Canada.
Christiane S. Rohr
Alberta Children’s Hospital Research Institute, University of Calgary, Calgary, AB, Canada; Child and Adolescent Imaging Research Program, University of Calgary, Calgary, AB, Canada; Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada
Robert E. Smith
The Florey Institute of Neuroscience and Mental Health, Melbourne, VIC, Australia; The Florey Department of Neuroscience and Mental Health, The University of Melbourne, Melbourne, VIC, Australia
Thijs Dhollander
The Florey Institute of Neuroscience and Mental Health, Melbourne, VIC, Australia; The Florey Department of Neuroscience and Mental Health, The University of Melbourne, Melbourne, VIC, Australia; Developmental Imaging, Murdoch Children’s Research Institute, Melbourne, VIC, Australia
Ivy Cho
Department of Psychological Clinical Sciences, University of Toronto, Toronto, ON, Canada
Catherine Lebel
Alberta Children’s Hospital Research Institute, University of Calgary, Calgary, AB, Canada; Child and Adolescent Imaging Research Program, University of Calgary, Calgary, AB, Canada; Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada; Owerko Centre, University of Calgary, Calgary, AB, Canada; Mathison Centre for Mental Health Research and Education, University of Calgary, Calgary, AB, Canada
Deborah Dewey
Alberta Children’s Hospital Research Institute, University of Calgary, Calgary, AB, Canada; Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada; Owerko Centre, University of Calgary, Calgary, AB, Canada; Department of Paediatrics, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada; Department of Community Health Sciences, University of Calgary, Calgary, AB, Canada
Alan Connelly
The Florey Institute of Neuroscience and Mental Health, Melbourne, VIC, Australia; The Florey Department of Neuroscience and Mental Health, The University of Melbourne, Melbourne, VIC, Australia
Signe Bray
Alberta Children’s Hospital Research Institute, University of Calgary, Calgary, AB, Canada; Child and Adolescent Imaging Research Program, University of Calgary, Calgary, AB, Canada; Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada; Owerko Centre, University of Calgary, Calgary, AB, Canada; Mathison Centre for Mental Health Research and Education, University of Calgary, Calgary, AB, Canada; Department of Radiology, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
Early childhood is an important period for cognitive and brain development, though white matter changes specific to this period remain understudied. Here we utilize a novel analytic approach to quantify and track developmental changes in white matter micro- and macro-structure, calculated from individually oriented fiber-bundle populations, termed “fixels”. Fixel-based analysis and mixed-effects models were used to assess tract-wise changes in fiber density and bundle morphology in 73 girls scanned at baseline (ages 4.09–7.02, mean = 5.47, SD = 0.81), 6-month (N = 7), and one-year follow-up (N = 42). For comparison, we also assessed changes in commonly utilized diffusion tensor metrics: fractional anisotropy (FA), and mean, radial and axial diffusivity (MD, RD, AD). Maturational increases in fixel-metrics were seen in most major white matter tracts, with the most rapid increases in the corticospinal tract and slowest or non-significant increases in the genu of the corpus callosum and uncinate fasciculi. As expected, we observed developmental increases in FA and decreases in MD, RD and AD, though percent changes were smaller relative to fixel-metrics. The majority of tracts showed more substantial morphological than microstructural changes. These findings highlight early childhood as a period of dynamic white matter maturation, characterized by large increases in macroscopic fiber bundle size, mild changes in axonal density, and parallel, albeit less substantial, changes in diffusion tensor metrics.
