The human brain experiences five distinct eras as we age, and each is defined by changes in our neural architecture that influence how we process information, new research shows. The brain changes associated with these stages shape how our mind ages and ultimately declines.
In a study published on Tuesday in Nature Communications, researchers compared the brain scans of 3,802 people between zero and 90 years old. By mapping the brain’s connections over time, the scientists detected four turning points in brain structure over the course of a human life: at age nine, 32, 66 and 83.
What this means, according to the researchers, is that our brain’s connections wire themselves in pretty much the same way from birth to nine years of age. Then our neural architecture starts to organize differently as we enter adolescence, continuing through age 32. At this point, the brain’s structural development appears to peak, according to the study.
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“What we find suggests that the journey from childlike brain development to this peak in the early 30s is distinct from other phases in the lifespan,” says Alexa Mousley, the study’s lead author and a neuroscientist at the University of Cambridge.
“This doesn’t mean that the brain of a 17-year-old and a 30-year-old look are the same—it’s specifically that the types of changes occurring ... are consistent,” she adds.
At age 32, the brain’s longest rewiring era begins, marking the opening of the adult years. It’s at this point that brain architecture starts to stabilize compared with the previous phases, and Mousley says this corresponds to past research that found that there is also a “plateau in intelligence and personality around this time.”
After the mid-60s, brain connections start to deteriorate. And by the last turning point, 83 years old, connectivity declines even further.
In a recent statement, Duncan Astle, a professor of neuroinformatics at Cambridge and a co-author of the study, said these epochs of brain development may mirror how humans experience changes over time.
“Looking back, many of us feel our lives have been characterised by different phases,” he said. “It turns out that brains also go through these eras.”
It’s unclear what these major shifts can tell us about learning and development in the brain, Mousley says. Past research has also pointed toward distinct phases of brain development through the lifespan, and it remains unclear how lifestyle factors or other variables may influence brain aging in individuals. And while the new study finds an obvious peak in efficiency in one’s early 30s, that could be linked to evolution, lifestyle changes or genetic factors.
“These are all just potential ideas—we truly don’t know,” she says.