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Development of cortical tissue during infancy is critical for the emergence of typical brain functions in cortex. However, how cortical microstructure develops during infancy remains unknown. We measured the longitudinal development of cortex from birth to six months of age using multimodal quantitative imaging of cortical microstructure. Here we show that infants’ cortex undergoes profound microstructural tissue growth during the first six months of human life. Comparison of postnatal to prenatal transcriptomic gene expression data demonstrates that myelination and synaptic processes are dominant contributors to this postnatal microstructural tissue growth. Using visual cortex as a model system, we find hierarchical microstructural growth: higher-level visual areas have less mature tissue at birth than earlier visual areas but grow at faster rates. This overturns the prominent view that visual areas that are most mature at birth develop fastest. Together, in vivo, longitudinal, and quantitative measurements, which we validated with ex vivo transcriptomic data, shed light on the rate, sequence, and biological mechanisms of developing cortical systems during early infancy. Importantly, our findings propose a hypothesis that cortical myelination is a key factor in cortical development during early infancy, which has important implications for diagnosis of neurodevelopmental disorders and delays in infants., To understand how cortical microstructure develops during infancy, Natu et al measure the longitudinal development of human sensory-motor cortex from birth to six months of age using multimodal quantitative neuroimaging. They show that cortical myelination is a key factor in brain development during early infancy, which could have implications for diagnosis of neurodevelopmental disorders and delay in infants.

The quality of the early environment influences the development of psychopathology. Children who are deprived of sufficient environmental enrichment in infancy may be at higher risk for developing symptoms of psychopathology in toddlerhood. In this study, we investigated the prospective association between naturalistic measures of adult language input obtained through passive monitoring of infants’ daily environments and emerging psychopathology in toddlerhood. In a sample of 100 mothers and their infants recruited from the community (mean age [range] = 6.73 [5-9] months), we used the Language ENvironment Analysis (LENA) system to measure multiple dimensions of infants’ language environments, including both the quantity and consistency of adult speech and conversational turns in infants’ daily lives as well as the quantity of infant vocalizations. Subsequently, during toddlerhood (mean age [range] = 18.29 [17-21] months), mothers reported on their children’s symptoms of psychopathology. Infants who experienced more consistent adult speech and conversational turns had lower symptoms of psychopathology in toddlerhood, independent of negative emotionality in infancy, maternal depressive symptoms, and laboratory-based measures of maternal sensitivity. These findings have implications for the measurement of environmental factors that may confer risk and resilience to emerging psychopathology.

This study utilized attachment theory as a framework for understanding how fathers' reflective functioning (RF) and social emotional (SE) and autonomy (AU) supportive behaviors relate to children's emotion regulation (ER) beyond effects of mothers' RF. Moreover, the study explored how fathers' RF may be a protective factor against risks associated with low income. Fathers (n = 77) and their toddlers participated. Fathers' RF was coded from narrative accounts of parenting and mothers' RF was assessed by questionnaire. Fathers' SE and AU supportive behaviors were coded from observations of father-child interactions; toddlers' ER was assessed as distress on a challenging task. Results show that, after accounting for mothers' RF, fathers' RF was directly associated with SE supportive behaviors; RF moderated the association between income and AU supportive behaviors. Fathers' SE and AU supportive behaviors were associated with children's distress. Fathers' RF plays a central role in parenting and in children's ER.