Cascading Periods of Language-Related Brain Plasticity Across Early Childhood.

Language is thought to have multiple sensitive periods in early childhood, but the neural basis of these sensitive periods is less understood. We leverage advances in in-vivo neuroimaging of plasticity, measuring the neural inhibition across the brain via Hurst exponent. Using two large datasets with children ages 10 months to 18 years (Baby Connectome Project: 10m-3y6m, 458 observations across n = 222 children; Human Connectome Project-Development: 5-18y, n = 437), we characterize the development of the Hurst exponent in language-related brain regions. In early childhood, Hurst increases in temporal and frontal language areas, and posterior regions develop earlier than anterior regions. In contrast, thalamic Hurst plateaus earlier, perhaps underlying the earliest language-related sensitive periods. Children with higher language-related skills show slower increases in cortical Hurst in early childhood, suggesting protracted plasticity. Later in childhood, cortical Hurst plateaus around age 9, suggesting a potential neural mechanism for age-related declines syntax learning. These results highlight a potential neural basis for cascading language-related sensitive periods.