Here are the five biggies
University of Cambridge
Neuroscientists at the University of Cambridge report that the human brain moves through five "major epochs" as it rewires itself from early development to late old age.
Each stage reflects a different
way the brain supports thinking, learning, and behavior as we grow, mature, and
eventually experience age-related decline.
A team from Cambridge's MRC Cognition and Brain Sciences
Unit analyzed MRI diffusion scans from 3,802 individuals ranging from newborns
to 90 years old. These scans track the movement of water through brain tissue,
which helps researchers map the networks that link one region to another.
Their findings, published in Nature Communications,
show that the brain's structure progresses through five broad phases. Four key
"turning points" divide these phases, marking ages when the brain
undergoes meaningful reorganization.
Childhood, Adolescence, and a Slow Path to Adulthood
The first epoch spans from birth to about age nine, when a
major turning point leads into the adolescent phase. This adolescent period
lasts much longer than expected, continuing until roughly age 32 on average.
In the early thirties, the brain's wiring shifts into an
adult configuration. This becomes the longest era and continues for more than
three decades. A third turning point near age 66 marks the beginning of an
"early aging" phase, while the final "late aging" stage
emerges around age 83.
"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," said Dr. Alexa Mousley, a Gates Cambridge Scholar who led the
research. "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."
Early Brain Growth: Synapses, Consolidation, and Rapid
Change
From infancy through childhood, the brain is shaped by
"network consolidation." Babies generate an enormous number of
synapses, the points where neurons communicate. Over time, only the most active
connections are kept while the rest are eliminated.
During this period, the entire brain follows a consistent
rewiring pattern. Grey and white matter grow quickly, pushing cortical
thickness (the distance between outer grey matter and inner white matter) to
its highest point. The folds of the cerebral cortex also stabilize, forming the
ridges seen on the outer surface.
By age nine, the brain encounters its first major turning
point. Cognitive abilities expand rapidly at this age, but the risk of
developing certain mental health conditions also becomes higher.
Adolescence: Increasing Efficiency and More Organized
Brain Networks
The second epoch, adolescence, is marked by continued growth
of white matter. As these pathways expand, the organization of communication
networks becomes more refined. MRI diffusion scans show more orderly water
movement in the tissue, reflecting stronger and more coordinated connections.
This period is notable for rising efficiency in how signals
move both within individual regions and across the whole brain. These
improvements are linked to gains in cognitive performance.
"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," said Mousley.
These changes peak in the early thirties, which researchers
describe as the "strongest topological turning point" across the
entire lifespan.
"Around the age of 32, we see the most directional
changes in wiring and 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."
Adulthood: Stability and Gradual Compartmentalization
At approximately age 32, the adult epoch begins. This phase
is relatively stable compared with earlier stages of life, and no additional
major turning points appear for about thirty years. According to the
researchers, this aligns with a "plateau in intelligence and
personality" described in other studies.
They also noted growing "segregation" during this
time, meaning that different brain regions begin to operate in more distinct
and specialized ways.
The next turning point, around age 66, is much more subtle.
While it does not involve dramatic structural changes, the team still observed
meaningful shifts in network organization.
"The data suggest that a gradual reorganization of
brain networks culminates in the mid-sixties," said Mousley. "This is
probably related to aging, 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."
Late Aging: Declining Global Connectivity and Regional
Reliance
The final turning point arrives near age 83, signaling the
start of the last brain structure epoch. Although the amount of data for this
phase is limited, researchers found a clear pattern. The brain becomes less
globally connected and depends more heavily on specific regions.
"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, Professor of
Neuroinformatics at Cambridge.
"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 behaviors."
"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 the Medical Research
Council, the Gates Foundation, and the Templeton World Charitable Foundation.Alexa
Mousley, Richard A. I. Bethlehem, Fang-Cheng Yeh, Duncan E. Astle. Topological
turning points across the human lifespan. Nature Communications,
2025; 16 (1) DOI: 10.1038/s41467-025-65974-8
