Poster No:
1030
Submission Type:
Abstract Submission
Authors:
Fumitaka Homae1, Daisuke Tsuzuki2
Institutions:
1Tokyo Metropolitan University, Tokyo, Japan, 2Kochi University, Kochi, Japan
First Author:
Co-Author:
Introduction:
The emergence of hemispheric asymmetry in the cerebral cortex is a central topic in cognitive neuroscience, as it underlies functional and physiological differences between the cerebral hemispheres (Chiron et al., 1997; Homae, 2014; Toga & Thompson, 2003). Structural asymmetries, such as greater cortical thickness in the right temporal regions of neonates (Li et al., 2015) and the prominence of the superior temporal sulcus in the right hemisphere of preterm infants (Dubois et al., 2008) and fetuses (Kasprian et al., 2011), have been observed early in brain development. While such structural asymmetries are well-documented, their underlying developmental mechanisms, particularly cortical myelination, remain less understood. Myelination is a critical process during early brain maturation and can be assessed using the T1-weighted/T2-weighted (T1w/T2w) ratio in magnetic resonance imaging (MRI) data, where higher ratios reflect greater cortical myelination (Glasser & Van Essen, 2011). Recent research using infant MRI datasets has demonstrated that regions of the right anterior temporal lobe exhibit higher T1w/T2w ratios compared to the left hemisphere (Bozek et al., 2018). However, the extent to which such hemispheric asymmetries in cortical myelination exist across multiple cortical regions and how these asymmetries vary with gestational age in preterm and full-term infants remains unclear. In this study, we analyze a large-scale infant MRI dataset to explore hemispheric differences in cortical myelination across six cortical regions and their progression with advancing gestational age.
Methods:
We analyzed cortical mesh data derived from infant MRI scans (Bozek et al., 2018; Makropoulos et al., 2018) using the second release of the Developing Human Connectome Project (Hughes et al., 2017). The dataset included brain images from very preterm infants (gestational age < 32 weeks, N = 72), preterm infants (gestational age < 37 weeks, N = 86), and full-term infants (N = 328). Infant data were categorized by scan week, ranging from 29 to 44 weeks in one-week intervals. For each hemisphere, mean T1w/T2w values were calculated across vertices in six cortical regions: the frontal, temporal, parietal, occipital, cingulate cortices, and the insula.
Results:
T1w/T2w values increased with gestational age across all cortical regions, though the rate of increase varied by region. Between 33 and 36 scan weeks, preterm infants showed higher T1w/T2w ratios than very preterm infants, while full-term infants exhibited the largest ratios between 38 and 42 weeks. Full-term infants reached a plateau in T1w/T2w values across all cortical regions during the scan weeks analyzed, and preterm infants' values converged with those of full-term infants by 44 weeks. Hemispheric asymmetry was observed in all infant groups: the parietal cortex, cingulate cortex, and insula showed comparable values between hemispheres, whereas the frontal, temporal, and occipital cortices exhibited higher values in the right hemisphere.
Conclusions:
This study revealed advanced myelination in the right hemisphere of the frontal, temporal, and occipital cortices, which was evident not only at full term (40 weeks) but also as early as 30 weeks in very preterm infants. Further investigation using fetal MRI data could clarify the origins of these hemispheric differences. Although T1w/T2w values increased with age in very preterm infants, they remained lower compared to preterm and full-term infants. Such developmental delays in cortical myelination are expected to diminish during childhood (Vandewouw et al., 2019); however, they could still have significant implications for early brain maturation. Identifying the mechanisms underlying these differences and their progression from infancy to early childhood is essential for understanding the relationship between cortical development and cognitive outcomes in individual infants.
Lifespan Development:
Normal Brain Development: Fetus to Adolescence 1
Neuroanatomy, Physiology, Metabolism and Neurotransmission:
Normal Development 2
Keywords:
Development
STRUCTURAL MRI
Other - asymmetry; infant; T1w/T2w
1|2Indicates the priority used for review
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Healthy subjects only or patients (note that patient studies may also involve healthy subjects):
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Was this research conducted in the United States?
No
Were any human subjects research approved by the relevant Institutional Review Board or ethics panel?
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Were any animal research approved by the relevant IACUC or other animal research panel?
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Please indicate which methods were used in your research:
Structural MRI
For human MRI, what field strength scanner do you use?
3.0T
Which processing packages did you use for your study?
Other, Please list
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dHCP pipelines
Provide references using APA citation style.
Bozek, J. (2018). Construction of a neonatal cortical surface atlas using Multimodal Surface Matching in the Developing Human Connectome Project. Neuroimage, 179, 11-29.
Chiron, C. (1997). The right brain hemisphere is dominant in human infants. Brain: a journal of neurology, 120(6), 1057-1065.
Dubois, J. (2008). Mapping the early cortical folding process in the preterm newborn brain. Cereb Cortex, 18(6), 1444-1454.
Glasser, M. F. (2011). Mapping human cortical areas in vivo based on myelin content as revealed by T1- and T2-weighted MRI. J Neurosci, 31(32), 11597-11616.
Homae, F. (2014). A brain of two halves: insights into interhemispheric organization provided by near-infrared spectroscopy. Neuroimage, 85 Pt 1, 354-362.
Hughes, E. J. (2017). A dedicated neonatal brain imaging system. Magn Reson Med, 78(2), 794-804.
Kasprian, G. (2011). The prenatal origin of hemispheric asymmetry: an in utero neuroimaging study. Cereb Cortex, 21(5), 1076-1083.
Li, G. (2015). Spatial Patterns, Longitudinal Development, and Hemispheric Asymmetries of Cortical Thickness in Infants from Birth to 2 Years of Age. J Neurosci, 35(24), 9150-9162.
Makropoulos, A. The developing human connectome project: A minimal processing pipeline for neonatal cortical surface reconstruction. Neuroimage, 173, 88-112.
Toga, A. W. (2003). Mapping brain asymmetry. Nat Rev Neurosci, 4(1), 37-48.
Vandewouw, M. M. (2019). Altered myelin maturation in four year old children born very preterm. Neuroimage Clin, 21, 101635.
No