Spatiotemporal Developmental Gradient of Thalamic Morphology, Microstructure, and Connectivity from the Third Trimester to Early Infancy.

Thalamus is a critical component of the limbic system that is extensively involved in both basic and high-order brain functions. However, how the thalamic structure and function develops at macro- and micro-scopic scales during the perinatal period development is not yet well characterized. Here, we used multi-shell high-angular resolution diffusion MRI of 144 preterm-born and full-term infants in both sexes scanned at 32 - 44 postmenstrual weeks (PMW) from the Developing Human Connectome Project (dHCP) database to investigate the thalamic development in morphology, microstructure, associated connectivity, and sub-nucleus division. We found evident anatomical expansion and linear increases of fiber integrity in the lateral side of the thalamus compared to the medial part. The tractography results indicated that thalamic connection to the frontal cortex developed later than the other thalamocortical connections (parieto-occipital, motor, somatosensory, and temporal). Using a connectivity-based segmentation strategy, we revealed that functional partitions of thalamic subdivisions were formed at 32 PMW or earlier, and the partition developed towards the adult pattern in a lateral-to-medial pattern. Collectively, these findings revealed faster development of the lateral thalamus than the central part as well as a posterior-to-anterior developmental gradient of thalamocortical connectivity from the third trimester to early infancy. SIGNIFICANCE: This is the first study that characterizes spatiotemporal developmental pattern of thalamus during the third trimester to early infancy. We found that thalamus develops in a lateral-to-medial pattern for both thalamic microstructures and subdivisions; and thalamocortical connectivity develops in a posterior-to-anterior gradient that thalamo-frontal connectivity appeared later than the other thalamocortical connections. These findings may enrich our understanding of the developmental principles of thalamus and provide references for the atypical brain growth in neurodevelopmental disorders.