Spatial Patterns, Longitudinal Development, and Hemispheric Asymmetries of Cortical Thickness in Infants from Birth to 2 Years of Age

Abstract

Cortical thickness (CT) is related to normal development and neurodevelopmental disorders. It remains largely unclear how the characteristic patterns of CT evolve in the first 2 years. In this paper, we systematically characterized for the first time the detailed vertex-wise patterns of spatial distribution, longitudinal development, and hemispheric asymmetries of CT at 0, 1, and 2 years of age, via surface-based analysis of 219 longitudinal magnetic resonance images from 73 infants. Despite the dynamic increase of CT in the first year and the little change of CT in the second year, we found that the overall spatial distribution of thin and thick cortices was largely present at birth, and evolved only modestly during the first 2 years. Specifically, the precentral gyrus, postcentral gyrus, occipital cortex, and superior parietal region had thin cortices, whereas the prefrontal, lateral temporal, insula, and inferior parietal regions had thick cortices. We revealed that in the first year thin cortices exhibited low growth rates of CT, whereas thick cortices exhibited high growth rates. We also found that gyri were thicker than sulci, and that the anterior bank of the central sulcus was thicker than the posterior bank. Moreover, we showed rightward hemispheric asymmetries of CT in the lateral temporal and posterior insula regions at birth, which shrank gradually in the first 2 years, and also leftward asymmetries in the medial prefrontal, paracentral, and anterior cingulate cortices, which expanded substantially during this period. This study provides the first comprehensive picture of early patterns and evolution of CT during infancy.

Keywords: cortical thickness; early brain development; hemispheric asymmetry; infant; spatial distribution; sulci and gyri.

Figure 1.

An illustration of reconstructed cortical surfaces for a neonatal MRI at 40.4 weeks of gestational age. a, Reconstructed inner (green) and outer cortical surface (red) overlaid on the T2-weighted MRI. b, Inner cortical surface color-coded by maximum principal curvature. c, Outer cortical surface color-coded by CT (in millimeters).

Figure 2.

Spatial distribution of CT of 73 infants at 0, 1, and 2 years of age. a, Vertex-wise maps of CT (in millimeters). b, Regions with CT significantly thicker (red clusters) or thinner (blue clusters) than the average thickness by TFCE (p < 0.01).

Figure 3.

Longitudinal development of CT of 73 infants in the first 2 years. a, Vertex-wise maps of thickness change percentage. b, Significant regions of thickness change by TFCE (p < 0.01).

Figure 4.

Scatter plots of CT growth percentage in the first year (y-axis) versus CT in millimeters (x-axis) at 0 year and 1 year at each 100th vertex (represented by a small circle) of the whole population.

Figure 5.

Means and SDs of CT on sulci, gyri, and whole cortex of each lobe at 0, 1, and 2 years of age (obtained from 73 infants).

Figure 6.

Percentages of CT on gyri larger than on sulci in the four lobes at 0, 1, and 2 years of age.

Figure 7.

Hemispheric asymmetries of CT at 0, 1, and 2 years of age. a, Asymmetry index of CT. b, Regions with significant CT asymmetries by TFCE (p < 0.01).

Figure 8.

Overlaying significant clusters of CT asymmetry onto the significant clusters of thick/thin cortices on the inflated surfaces at 0, 1, and 2 years of age.

Figure 9.

Scatter plots of CT differences between left and right hemispheres with longitudinal information in the representative significant regions at 0, 1, and 2 years of age.

Figure 10.

Overlaying the significant clusters of SA asymmetries onto the significant clusters of CT asymmetries at 0, 1, and 2 years of age.