Scientists have identified five major 'epochs' of human brain development, according to one of the most comprehensive studies of how neural wiring changes from infancy to old age. The research, based on brain scans of nearly 4,000 people aged under one to 90, mapped neural connections and their evolution throughout life.
The study revealed four pivotal 'turning points' when brain organisation shifts to a different trajectory, at approximately ages nine, 32, 66 and 83 years. These transitions separate the childhood, adolescent, adult, early ageing and late ageing phases of brain architecture.
From infancy to age nine, the brain is defined by 'network consolidation', where the number of synapses is reduced and active ones survive. During this period, wiring efficiency decreases while grey and white matter grow rapidly, with cortical thickness reaching a peak and folding stabilising.
The adolescent epoch lasts until around age 32, during which white matter continues to grow and brain connection efficiency steadily increases, linked to enhanced cognitive performance. The strongest shift occurs at about 32, when brain architecture stabilises and regions become more compartmentalised, corresponding to a plateau in intelligence and personality.
The final two turning points, at 66 and 83, are marked by decreases in brain connectivity, believed to be related to ageing and degeneration of white matter. Researchers say understanding these critical periods could help identify when the brain's wiring is vulnerable to disruption, offering insights into mental health disorders that often emerge in adolescence.
