Researchers have outlined five separate phases of brain development and decline, spanning from early childhood through late life. One of the most notable findings is an extended adolescent period in the brain that stretches roughly from age 9 to 32.
Experts at the University of Cambridge analyzed MRI data from about 3,800 neurotypical individuals, whose ages ranged from newborns to 90 year olds. Their work highlights key transition points at approximately 9, 32, 66, and 83 years of age, when the brain undergoes major structural shifts to support changing cognitive needs.
The study, led by Dr. Alexa Mousley, is described as the first to map major wiring phases of the human brain across an entire lifespan. Using MRI tractography, the team tracked how neural pathways grow, reorganize, and deteriorate over time. Mousley suggests that these insights could contribute to a better understanding of atypical brain development and disorders such as dementia.
Childhood: Birth to Age 9
During childhood, the brain is in an intensive growth phase. It generates billions of new connections while simultaneously undergoing synaptic pruning, a process that strengthens essential pathways and removes weaker ones. Imaging shows distinct firing directions in developing neurons, illustrating how various regions begin forming complex communication networks.
Adolescence: Ages 9 to 32
Adolescence in the brain is far longer than the social definition of teenage years. Between ages 9 and 32, the brain continually refines its internal and interregional communication. Neural networks become more efficient and better synchronized. Mousley told The Guardian that this does not imply adults in their late twenties behave like teenagers, but rather that structural maturation continues well into early adulthood.
Adulthood: Around Age 32
By about age 32, the brain reaches its adult form. Intelligence and personality stabilize, and neural efficiency is near its peak. This phase marks a shift to a more organized and less flexible neural system, a state that tends to remain steady for several decades. Senior researcher Professor Duncan Astle notes that identifying these key turning points may help scientists learn when the brain is most vulnerable to disruption.
Early Aging: Around Age 66
Around the mid sixties, signs of early aging begin to appear. The brain gradually loses volume and undergoes a reorganization of its networks. Connectivity between different regions diminishes, and reduced blood flow increases vulnerability to age related conditions.
Advanced Aging: After Age 83
In the final phase, starting around age 83, brain connectivity declines more sharply. White matter, which played a major role in forming broad neural networks earlier in life, noticeably diminishes. The brain becomes more dependent on a limited set of regions as its overall flexibility decreases.
Professor Tara Spires Jones from the University of Edinburgh, who was not involved in the study, noted that the findings align with current scientific understanding of brain aging. She added that individuals may experience these transitions at slightly different times.
