The brain has five major structural phases during the human lifespan and doesn’t reach adulthood until age 32, a new study suggests.
Scientists determined that brain development is defined by four “turning points” — at ages 9, 32, 66 and 88 — by analyzing brain scans from more than 3,800 people ages 0-90. Their findings, published Tuesday in Nature Communications, could have implications for better understanding issues that affect brain health at different stages of life, the researchers said.
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“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,” said Duncan Astle, the study’s senior author and a professor of neuroinformatics at Cambridge University in England.
In particular, the scientists defined five life stages:
• Childhood as birth to 9
• Adolescence as 9 to 32
• Adulthood as 32 to 66
• Early aging as 66 to 83
• Late aging as 83 on
“These eras provide important context for what our brains might be best at, or more vulnerable to, at different stages of our lives,” Cambridge researcher Alexa Mousley said. “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.”
Here’s what happens at each of the five stages:
Childhood
During childhood, the brain has an abundance of synapses – links between nerve cells that enable them to communicate with each other. But over the first nine years of life, those synapses reduce, with the strongest ones surviving. At the same time, the brain itself is growing.
Adolescence
Age 9, the first “turning point” in brain development, is marked by changes in how much information the brain can store at any one moment, as well as by a higher risk of developing mental health issues, the study found.
Adolescence begins with the onset of puberty, but ends much later than previously thought – extending even past the mid-20s which neuroscience has more recently identified – into the early 30s, researchers found.
During this period, communication networks in the brain become much faster and more efficient, and cognitive performance improves.
“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,” Mousley said.
Adulthood
The adult era, stretching across the span of more than 30 years, is the longest “epoch” in the human lifespan and the most stable. As previous research has found, there is a “plateau in intelligence and personality,” the researchers found.
Early aging
This is a time when brain reorganization reaches its highest point before beginning to decline. Brain regions become more tightly organized into different sections that operate in a less connected way than previously. During this stage, people face increased risk for health issues affecting the brain, such as high blood pressure.
Late aging
During this final epoch, brain connectivity declines further, with a shift from “global to local,” the researchers said. Less data is available for this era of development.