Timeline of human brain development

The human brain development timeline encompasses the sequential, overlapping phases in which the central nervous system forms, matures, and reorganizes from conception through adolescence and into early adulthood. This process starts in the third gestational week with the differentiation of neural progenitor cells and progresses through neurogenesis, cell migration, synaptogenesis, myelination, and synaptic pruning.

Many foundational structures of the brain, including the forebrain, midbrain, and hindbrain, emerge by the sixth week of gestation, with further differentiation resulting in secondary regions like the telencephalon, diencephalon, and metencephalon in subsequent weeks. Structural milestones, including the formation of cortical folds and the appearance of commissural fibers, occur rapidly during prenatal development.

Postnatally, white matter volume and grey matter architecture undergo significant changes, with cortical regions maturing at different rates. The frontal and parietal lobes tend to mature earlier than temporal regions, with synaptic pruning and myelination continuing into the fourth decade of life. Experience and environmental factors dynamically shape neural connectivity, influencing lifelong cognitive, affective, and behavioral outcomes.

Advances in magnetic resonance imaging and the study of brain organoids have enhanced understanding of neurological disorders and critical periods of vulnerability, enabling new approaches for early diagnosis and intervention.