The human brain undergoes five major shifts in its wiring from infancy to old age, with its most dramatic reorganization occurring around age 32 rather than in adolescence, according to a large Cambridge study of more than 3,800 MRI scans.
The study, led by researchers at Cambridge’s MRC Cognition and Brain Sciences Unit, analyzed MRI diffusion scans from 3,802 people aged between birth and 90.
Published in Nature Communications on Tuesday, it offers the most comprehensive picture to date of how neural connections reorganize as we grow, mature, and age.
"This study is the first to identify major phases of brain wiring across a human lifespan,” Dr. Alexa Mousley, a Gates Cambridge Scholar who led the research, said in a statement.
She said these insights "provide important context for what our brains might be best at, or more vulnerable to, at different stages of our lives.”
The team found childhood brain topology runs from birth to about nine, marked by rapid growth in grey and white matter and a pruning of early synapses.
The shift into adolescence brings increasingly efficient networks, with white-matter organization peaking in the early 30s.
"Around the age of 32, we see the most directional changes in wiring and the largest overall shift in trajectory,” said Mousley.
This point marks the beginning of the long adult era, a period of stability that lasts more than three decades.
Researchers say this phase corresponds with a broad "plateau in intelligence and personality.”
A gentler turning point arrives around 66, when early aging begins.
"The data suggest that a gradual reorganization of brain networks culminates in the mid-sixties,” said Mousley, linking it to declining white matter and increased health risks such as hypertension.
The final epoch starts at roughly 83, as global connectivity wanes and the brain relies more on local networks.
"Looking back, many of us feel our lives have been characterized by different phases. It turns out that brains also go through these eras,” said senior author Prof. Duncan Astle.
