Institution: Stanford University
Talk Title: Infants’ cortex undergoes microstructural growth coupled with myelination during development
Abstract: The establishment of neural circuitry during early infancy is critical for developing complex sensory and motor functions. However, how cortical tissue develops postnatally is largely unknown. By combining structural MRI and quantitative MRI measure (R1) in infants, we tracked cortical tissue development across 3 time-points (newborn, 3 months, and 6 months). Higher R1 indicates higher microstructural tissue density and more developed cortex. Our data reveal three main findings: First, primary sensory/motor areas (V1: visual, A1: auditory, S1: somatosensory, M1: motor) have higher R1 at birth than higher-level cortical areas. However, all primary areas show significant increase in R1 in first six months of life, illustrating profound tissue growth after birth. Second, significant increase in R1 in newborns to 6-month-olds occurs in all visual areas of the ventral and dorsal visual streams. Strikingly, this development is heterogenous across the visual hierarchies: Earlier areas are more developed with denser tissue at birth than higher-order areas, but higher-order areas have faster rates of development. Finally, analysis of transcriptomic gene data that compares gene expression in postnatal vs. prenatal tissue samples showed strong postnatal expression of genes associated with myelination, synaptic signaling, and dendritic processes. Our results indicate that these cellular processes may contribute to profound postnatal tissue growth in the visual cortex observed in our in-vivo measurements. We propose a novel principle of postnatal maturation of sensory systems: development of cortical tissue proceeds in a hierarchical manner, enabling the lower-level areas to develop first to provide scaffolding for higher-order areas, which begin to develop more rapidly following birth to perform complex computations for sensory-motor processes.