A recent study conducted by the MRC Cognition and Brain Sciences Unit at the University of Cambridge has identified five distinct phases in human brain structure throughout a lifetime. The research, published in Nature Communications, analyzed MRI diffusion scans from 3,802 individuals ranging from newborns to 90-year-olds. These scans map neural connections by observing how water molecules move through brain tissue.
Researchers discovered that the human brain undergoes four key "turning points" that separate five broad structural phases. The first phase, characterized as childhood topology, lasts from birth until about age nine. At this point, the brain transitions into an adolescent phase that continues until approximately age 32.
Dr Alexa Mousley, a Gates Cambridge Scholar who led the study, said: “We know the brain’s wiring is crucial to our development, but we lack a big picture of how it changes across our lives and why.” She added: “This study is the first to identify major phases of brain wiring across a human lifespan.”
“These eras provide important context for what our brains might be best at, or more vulnerable to, at different stages of our lives. It could help us understand why some brains develop differently at key points in life, whether it be learning difficulties in childhood, or dementia in our later years.”
During infancy and childhood, researchers observed a process called "network consolidation," where excess synapses are pruned and active ones are retained. This period also sees rapid growth in grey and white matter volume. By age nine—the first turning point—children experience increased cognitive capacity alongside heightened vulnerability to mental health issues.
The adolescent phase is marked by continued white matter growth and increasing efficiency in both regional and whole-brain communication networks. According to Mousley: “Neural efficiency is as you might imagine, well connected by short paths, and the adolescent era is the only one in which this efficiency is increasing.”
Researchers noted that early thirties mark the strongest shift in brain wiring during a lifetime. “Around the age of 32, we see the most directional changes in wiring and the largest overall shift in trajectory, compared to all the other turning points,” said Mousley.
“While puberty offers a clear start, the end of adolescence is much harder to pin down scientifically. Based purely on neural architecture, we found that adolescent-like changes in brain structure end around the early thirties.”
From age 32 onward begins adulthood—the longest era—characterized by relative stability in brain architecture for over three decades. During this time there are no major structural shifts; instead regions become increasingly compartmentalized.
At around age 66—a milder turning point—there are gradual reorganizations within brain networks associated with aging and reduced connectivity as white matter degenerates. Mousley explained: “The data suggest that a gradual reorganisation of brain networks culminates in the mid-sixties… This is probably related to ageing, with further reduced connectivity as white matter starts to degenerate… This is an age when people face increased risk for a variety of health conditions that can affect the brain, such as hypertension.”
The final phase starts near age 83 when global connectivity declines further and reliance on specific regions increases.
Senior author Professor Duncan Astle commented: “Looking back, many of us feel our lives have been characterised by different phases. It turns out that brains also go through these eras.”
“Many neurodevelopmental, mental health and neurological conditions are linked to the way the brain is wired. Indeed, differences in brain wiring predict difficulties with attention, language, memory, and a whole host of different behaviours”
“Understanding that the brain’s structural journey is not a question of steady progression, but rather one of a few major turning points will help us identify when and how its wiring is vulnerable to disruption.”
The research received support from organizations including the Medical Research Council (MRC), Gates Foundation and Templeton World Charitable Foundation.