Postnatal critical-period brain plasticity and neurodevelopmental disorders: revisited circuit mechanisms

Critical periods (CPs) are defined as postnatal developmental windows during which brain circuits exhibit heightened sensitivity to altered experiences or sensory inputs, particularly during brain development in humans and animals. During the CP, experience-induced refinements of neural connections are crucial for establishing adaptive and mature brain functions, and aberrant CPs are often accompanied by many neurodevelopmental disorders (NDDs), including autism spectrum disorders and schizophrenia. Understanding neural mechanisms underlying the CP regulation is key to delineating the etiology of NDDs caused by abnormal postnatal neurodevelopment. Recent evidence from studies using innovative experimental tools has continuously revisited the inhibition-gating theory of CP to systematically elucidate the differential roles of distinct inhibitory circuits. Here, we provide a comprehensive review of classical experimental findings and emerging inhibitory-circuit regulation mechanisms of the CP, and further discuss how aberrant CP plasticity is associated with NDDs.