Abstract
Cortical maturation, including age-related changes in thickness, volume, surface area, and folding (gyrification), play a central role in developing brain function and plasticity. Further, abnormal cortical maturation is a suspected substrate in various behavioral, intellectual, and psychiatric disorders. However, in order to characterize the altered development associated with these disorders, appreciation of the normative patterns of cortical development in neurotypical children between 1 and 6 years of age, a period of peak brain development during which many behavioral and developmental disorders emerge, is necessary. To this end, we examined measures of cortical thickness, surface area, mean curvature, and gray matter volume across 34 bilateral regions in a cohort of 140 healthy children devoid of major risk factors for abnormal development. From these data, we observed linear, logarithmic, and quadratic patterns of change with age depending on brain region. Cortical thinning, ranging from 10% to 20%, was observed throughout most of the brain, with the exception of posterior brain structures, which showed initial cortical thinning from 1 to 5 years, followed by thickening. Cortical surface area expansion ranged from 20% to 108%, and cortical curvature varied by 1–20% across the investigated age range. Right-left hemisphere asymmetry was observed across development for each of the 4 cortical measures. Our results present new insight into the normative patterns of cortical development across an important but under studied developmental window, and provide a valuable reference to which trajectories observed in neurodevelopmental disorders may be compared.
Highlights
Human cortical development is a complex process comprising both gross morphometric change and microstructural progressions
In this work we have sought to bridge the knowledge gap in cortical maturation that currently exists between infants and neonates (Gilmore et al, 2012; Knickmeyer et al, 2008; Lyall et al, 2015) and later childhood/adolescence (Raznahan et al, 2011; Shaw et al, 2008; Sowell et al, 2004) by characterizing patterns of cortical growth from 1 to 6 years of age
Results of our analysis reveal that cortical thickness, surface area, curvature, and volume change with age throughout early childhood, exhibiting region specific developmental trajectories and asymmetries
Summary
Human cortical development is a complex process comprising both gross morphometric change and microstructural progressions. Advancement of the cortical myeloarchitecture contributes to the changing microstructure and morphology, and is associated with developing brain function and neuroplasticity (Brody et al, 1987; Leipsic, 1901; Yakovlev and Lecours, 1967) These morphometric and microstructural changes can be observed on MRI, and can be indirectly quantified by metrics including cortical thickness, surface area, volume, and curvature (Croteau-Chonka et al, 2016; Deoni et al, 2015; Grydeland et al, 2013). Across early development, cortical maturation exhibits regionally-specific asymmetry between the left and right hemispheres (Li et al, 2014; Nie et al, 2014) These changes continue throughout childhood and adolescence, with cortical thickness following different trajectories of thinning depending on region, cortex type (Shaw et al, 2008), and gender (Sowell et al, 2004)
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