Neurodevelopment is the process by which the nervous system forms, organizes and matures from early embryonic stages through adulthood. It begins with the specification of neural tissue, followed by the formation of the neural tube, which later gives rise to the brain and spinal cord. Neural stem and progenitor cells proliferate, then differentiate into neurons and glial cells in tightly regulated spatial and temporal patterns.

A key feature of neurodevelopment is neuronal migration, where immature neurons travel from their birthplace to final positions, establishing the layered structure of the cortex and other brain regions. Once positioned, neurons extend axons and dendrites, guided by molecular cues that attract or repel growing fibers. This wiring process creates functional circuits that underlie sensory processing, motor control, cognition and emotion.

Synaptogenesis dramatically increases the number of connections during prenatal and early postnatal life. Later, activity dependent synaptic pruning removes weaker connections and stabilizes stronger ones, refining network efficiency. Myelination by oligodendrocytes improves conduction speed and continues well into adolescence and early adulthood, particularly in association cortices involved in complex cognition.

Neurodevelopment is shaped by both genes and environment. Genetic programs control cell fate, migration and connectivity, while experience and sensory input modify synaptic strength and circuit organization. Critical periods are windows of heightened plasticity when specific experiences are especially influential. Disruptions in any of these steps, due to genetic variants, toxins, infections, malnutrition or stress, can alter brain architecture and lead to neurodevelopmental conditions such as autism spectrum disorder, attention deficit hyperactivity disorder and intellectual disability. Understanding these mechanisms provides targets for early detection, intervention and potential therapies.