Five newly discovered life stages of your brain include a prolonged adolescence from age 9 to 32

• Scientists have pinpointed five different "eras" of brain aging, from childhood to old age.
• The eras include a prolonged "adolescent" brain phase that lasts from about age 9 to 32.
• "This is a very cool study," another brain scientist said.

Your brain goes through five distinct life stages as you age, with a massive teenager phase from nine to 32.

Scientists at the University of Cambridge's cognition and brain sciences unit have used images of roughly 3,800 "neurotypical" brains, ranging in age from birth to 90, to pinpoint these turning points where our brains change shape to serve different functions as we grow, age, and eventually decline.

Roughly speaking, ages nine, 32, 66, and 83 mark pivotal shifts in how our brains operate.

"This study is the first to identify major phases of brain wiring across a human lifespan," Dr. Alexa Mousley, who led the research, said in a release. The study used MRI tractography to map how nerve fibers shift, grow, and die throughout our lifetimes.

Mousley said the findings may "help us understand why some brains develop differently," and lead to a deeper understanding of neurodegenerative conditions like dementia.

Scientists have mapped out a precise timeline for when your brain transitions from child to adult, and from healthy into decline

Childhood: 0-9

From birth to age nine, the brain is in growth mode. Billions of connections are generated.

There is a ton of what neuroscientists call synaptic "pruning" and consolidation happening, as important brain connections are strengthened, while weaker synapses die off.

The different colors here show different directions that the neurons are firing: up-down, side-to-side, and front-to-back, revealing which parts of the brain are making connections.

Adolescence: 9-32

Adolescence is a multi-decade process in the brain, lasting from about age nine to 32. During this time, there's more refinement of brain communication, both inside and between different brain regions. Our brain becomes more efficient and integrated.

"We're definitely not saying that people in their late 20s are going to be acting like teenagers, or even that their brain looks like that of a teenager," Mousley told The Guardian. It's just that adolescent-like changes to our brain structure, with more and more neural efficiency over time, continue until our early thirties.

Adulthood: 32-66

By 32, our brain is an adult. The early thirties serve as a major turning point for the brain, structurally speaking. Our intelligence and personality stabilize, efficiency is near-peak, and the brain settles into a less dynamic and more compartmentalized, business-like era that will last for more than 30 years.

"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," senior study author Duncan Astle, a professor of neuroinformatics at Cambridge, said in a release.

Early aging: 66-83

At around age 66, things start to noticeably degenerate, in what the scientists call "early aging."

While the brain subtly shrinks, there is a "gradual reorganization" of the brain networks, Mousley said. There is less connectivity between different brain regions, and more disease risk, as blood flow decreases.

Late aging: 83+

Finally, by 83 years old, brain connectivity is in sharper decline. The white matter that was overabundant in childhood, so critical for making diverse connections between different areas of the brain, is fading, and there's a deeper reliance on a few specific brain regions.

Professor Tara Spires-Jones, who directs the centre for discovery brain sciences at the University of Edinburgh, and who was not involved in this research, told the BBC "this is a very cool study" that fits well with what neuroscientists already understand about the aging brain. Still, "not everyone will experience these network changes at exactly the same ages," she said.