by The human brain goes through five distinct stages of development over the average human lifetime, with measurable key turning points as we grow, mature, age and decline, new research shows.
Neuroscientists at the University of Cambridge scanned the brains of nearly 4,000 people aged 0 to 90 to identify the four milestones that mark fundamental changes in the neural connections that make our brains function.
One of the most surprising findings is that the period that scientists call “adolescence” begins around the age of nine, but far from ending when you reach your twenties, it continues for another decade until you reach your early 30s.
The research results published in the journal nature communication, found that our brains are constantly learning and adapting as we absorb new information. However, it is not a smooth path of growth and consolidation, but one characterized by hectic activity – especially in the first half of life.
The five “major eras” the team identified are:
Childhood – from birth to nine years of age
Youth – from nine to 32
Adulthood – from 32 to 66
Early aging – from 66 to 83
Late ripening – from 83
These different epochs were discovered using datasets from MRI diffusion scans, which map neuronal connections in the brain by tracking how water molecules move through brain tissue.
“We know that brain wiring is critical to our development, but we lack a comprehensive picture of how it changes in our lives and why,” said Dr. Alexa Mousley, a Gates Cambridge Fellow who led the research.
“These eras provide important context for what our brains do best or are 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 learning difficulties in childhood or dementia in our later years.”
childhood
During the first epoch, which runs from birth through childhood to around age nine, our brains are defined by “network consolidation,” the team’s research found. During this process, the abundance of synapses—the connections between neurons—that are overproduced in a baby’s brain is reduced, so only the more active ones survive.
At the end of the first era, the brain experiences a dramatic change in cognitive performance, but this is accompanied by vulnerability, as the team says that from this point onwards there is also an increased risk of mental disorders.
“Many of us feel that our lives are characterized by different phases. It turns out that the brain also goes through these phases” (Dr. Alexa Mousley, University of Cambridge)
youth
During adolescence, the brain’s communication networks become increasingly sophisticated, brain scans showed.
This phase is characterized by the development of faster and smoother communication both within specific brain areas and throughout the brain – a transformation that drives the transition to much stronger cognitive abilities.
The team said this process is typically not complete until one’s early thirties.
adulthood
From around the age of 32, the longest period begins, that of adulthood. The brain architecture stabilizes compared to previous phases – with no major turning points for another thirty years.
This corresponds to a “plateau in intelligence and personality” based on other studies, the research team said.
They also found that “segregation” is more pronounced during this era, as regions of the brain slowly begin to become less connected and more compartmentalized.
Early aging
“The data suggest that a gradual reorganization of brain networks peaks in the mid-1960s,” said Dr. Mousley. “This is likely related to age, with connectivity continuing to decline as white matter begins to degenerate.
She said this is also a time “when people are at increased risk for a variety of health conditions that can affect the brain, such as high blood pressure.”
Late aging
The final epoch of brain structure begins at around age 83.
The team said the defining feature is “a shift from global to local” as inter-regional brain connectivity declines even further. People now tend to rely more and more on certain well-worn nerve pathways and regions.
MRI scans of the human brain – the only organ believed to have ever given itself a name (Getty Images)
Duncan Astle, professor of neuroinformatics at Cambridge, said the team’s study will help understand the different vulnerabilities of the brain at different stages of development and minimize risks and treat certain diseases.
“Looking back, many of us feel that our lives have been characterized by different phases. It turns out that the brain also goes through these phases,” he said.
“Many neurodevelopmental, mental health, and neurological diseases are related to the way the brain is wired. In fact, differences in brain wiring reveal difficulties in attention, language, memory, and a whole range of different behaviors.”
He added: “If we understand that the brain’s structural development is not a matter of steady progress, but rather one of the few major turning points, we can see when and how its wiring is vulnerable to disruption.”
