Key Phases of Brain Development from Childhood to Late Life
RESEARCHERS have charted how the brain’s structural networks develop from birth to 90 years old, revealing five key phases of topological change. Using diffusion imaging from over 4,200 participants and advanced graph theory analyses, they identified four major turning points, around ages 9, 32, 66, and 83 years, where brain network organisation shifts substantially. These findings highlight the non-linear, dynamic nature of brain development and aging.
Epoch 1: Infancy into Childhood (0–9 years)
The first epoch covers infancy through early childhood and is marked by rapid brain growth and synaptic pruning. Although overall network integration decreases, connections between neighbouring regions strengthen, creating locally efficient networks. Around 9 years old, a major turning point occurs: the brain begins to reorganise in preparation for adolescence. This aligns with puberty onset and key cognitive, emotional, and behavioural milestones, including heightened learning potential and emerging mental health vulnerabilities.
Epoch 2: Adolescence to Early Adulthood (9–32 years)
Between ages 9 and 32, the brain’s networks become increasingly integrated and efficient. This phase corresponds with late childhood, adolescence, and early adulthood. White matter volume and integrity peak, facilitating more coordinated and globally connected networks. Centrality, how influential certain brain regions are within the network, plays a critical role during this period, supporting cognitive and emotional maturation. By around 32 years, brain topology shifts again, reflecting the transition into the stability of adult networks.
Epoch 3: Adulthood (32–66 years)
During adulthood, network changes slow, with modest decreases in global integration and increases in segregation. This stable period corresponds with peaks in intelligence, personality consolidation, and relative cognitive consistency. While structural brain changes are subtler, local efficiency and modular organisation continue to refine processing and information flow.
Epoch 4: Early Ageing (66–83 years)
In early aging, the brain exhibits increasing modularity and selective reorganisation, alongside declines in white matter integrity. This simplification of network architecture coincides with heightened risk of age-related cognitive changes, including hypertension-related cognitive decline and early dementia onset. Despite these changes, many adults maintain cognitive function due to resilient local network connectivity.
Epoch 5: Late Ageing (83–90 years)
The final epoch shows further reduction in overall brain network connectivity. Only specific nodes retain importance, reflecting targeted local network activity. This decline in age-topology relationship suggests a natural slowing of brain plasticity in late life, although individual differences remain significant.
Implications for Brain Health
By delineating these five lifespan epochs, the study provides a roadmap for understanding cognitive development, learning potential, and the ageing brain. Recognising when network reorganisation occurs may guide interventions to support mental health, learning, and healthy ageing throughout life.
Reference
Mousley A et al. Topological turning points across the human lifespan. Nat Commun. 2025;16(1):10055.
