Infant brain regional cerebral blood flow increases supporting emergence of the default-mode network

Abstract

Human infancy is characterized by most rapid regional cerebral blood flow (rCBF) increases across lifespan and emergence of a fundamental brain system default-mode network (DMN). However, how infant rCBF changes spatiotemporally across the brain and how the rCBF increase supports emergence of functional networks such as DMN remains unknown. Here, by acquiring cutting-edge multi-modal MRI including pseudo-continuous arterial-spin-labeled perfusion MRI and resting-state functional MRI of 48 infants cross-sectionally, we elucidated unprecedented 4D spatiotemporal infant rCBF framework and region-specific physiology–function coupling across infancy. We found that faster rCBF increases in the DMN than visual and sensorimotor networks. We also found strongly coupled increases of rCBF and network strength specifically in the DMN, suggesting faster local blood flow increase to meet extraneuronal metabolic demands in the DMN maturation. These results offer insights into the physiological mechanism of brain functional network emergence and have important implications in altered network maturation in brain disorders.

Spatiotemporal cerebral blood flow dynamics underlies emergence of the limbic-sensorimotor-association cortical gradient in human infancy

“…Our findings were further supported by a validation analysis of voxel-wise age effects using rCBF maps ( N = 48) obtained from cohort-2 (Beijing site) 30 . The age effects were highly reproducible in both infant rCBF datasets, showing similar spatial topographies (Supplementary Fig.…”

“…9 . The identified physiological hierarchy aligns well with the pronounced and qualitatively distinct regional differences in infant functional connectivity 20–22,30 , neuroanatomy 2,16,43 , and transcriptomic profile 44,45 . For instance, limbic and primary sensorimotor functional networks are relatively well established at birth 20,21 .…”

“…For instance, limbic and primary sensorimotor functional networks are relatively well established at birth 20,21 . In contrast, functional networks involving association cortices (e.g., default mode, frontoparietal, and attention networks) are often recognizable in topographically incomplete forms at birth and then grow rapidly during the first two years of life 22,30 , gradually establishing the limbic-sensorimotor-association functional gradient. Thus, it is not surprising that rCBF rises greatly in these association cortices to meet the extra energy demand for functional network and gradient formation 30 .…”

“…The labeling efficiency α and T 1a could vary considerably across participants, especially in infants. Thus, we used global CBF from PC-MRI to calibrate rCBF measures from pCASL, as described previously 28,30,57 . Specifically, rCBF was calibrated by applying the scalar factor making averaged rCBF equal to global CBF.…”

Not with a “zap” but with a “beep”: Measuring the origins of perinatal experience

“…Similarly, two recent, large sampled fMRI studies of newborns found evidence of DMN connectivity mere weeks after birth (Hu et al, 2022;Sylvester et al, 2022). Furthermore, increasing functional connectivity within the DMN is supported by increases in regional cerebral blood flow in the first two years of life (Yu et al, 2023). The DMN present during the perinatal period might be interpreted as a weaker, immature version of the adult DMN, as Hu et al (2022) found that the neonatal DMN and other fMRI networks had less within-network connectivity compared to adults.…”