Your brain changes at 9, 32, 66, and 83
A team of neuroscientists from the University of Cambridge in the United Kingdom has identified five major phases of brain structure over the course of an average human life. These eras occur as the human brain rewires itself to support different ways of thinking as we grow, mature, and ultimately decline. The five major turning points are detailed in a study published today in the journal Natural communications.
In the study, they compared the brains of 3,802 people aged zero to 90, using diffusion MRI datasets. These types of MRI scans map neuronal connections by tracking how water molecules move through brain tissue. They detected five major phases of brain structure in the average human life, divided by four crucial turning points between birth and death when our brains reconfigure themselves.
The major turning points occur at times:
- Nine (childhood brain architecture)
- 32 (Brain architecture in adulthood)
- 66 (early aging)
- 83 (Late aging)
“We know that the brain’s wiring is crucial for our development, but we don’t have a comprehensive idea of how it changes over the course of our lives and why,” study co-author and neuroscientist Dr. Alexa Mousley said in a statement. “This study is the first to identify key phases of brain wiring throughout the human lifespan. These eras provide important context for what our brains might be best or most vulnerable to at different stages of our lives. This could help us understand why some brains develop differently at key times in life, whether it’s learning difficulties in childhood or dementia in our later years.”
Nine years – From baby to child
From infancy to early childhood, the brain is defined by the consolidation of networks. All the connectors between neurons, called synapses, which were overproduced in the baby’s brain, diminish. The most active synapses survive, shaping the brain’s primitive architecture.
Throughout the brain, these connections reconnect in the same pattern from birth until around age nine. During this time, the gray and white matter of the brain rapidly increases in volume.
The child’s brain functions from birth until a turning point at age nine. Here, the brain experiences a change in its cognitive abilities, but also an increased risk of mental health disorders.
32 years old – The adult brain takes shape
In your early 30s, the brain’s neural wiring shifts into adult mode. White matter continues to grow in volume, so the brain’s communication networks are increasingly refined based on MRI scans showing how water molecules move. These changes maintain the brain at an enhanced level of cognitive performance that peaks in the early 30s and constitutes the brain’s “most important topological turning point” of the entire lifespan, according to the team.
“Around age 32, we see the greatest number of changes in wiring direction and the greatest overall change in trajectory, compared to all other turning points,” Mousley said. “While puberty provides a clear start, the end of adolescence is much more difficult to pin down scientifically. Based on neural architecture alone, we found that changes in adolescent-like brain structure end around the early 30s.”
Adulthood is the longest period and lasts three decades. The architecture of the brain is also stabilizing compared to previous phases, with no major turning point in the next 30 years. According to the team, this corresponds to a “plateau of intelligence and personality”.
Dr Alexa Mousley, University of Cambridge
66 years old – Start of early aging
This turning point in the mid-1960s marks the beginning of a phase of “early aging” of brain architecture. This is a gentler period and one not defined by any major structural changes. However, the team still found significant changes in the configuration of brain networks on average around the age of 66.
“The data suggest that a progressive reorganization of brain networks peaks in the mid-sixties,” Mousley said. “This is likely linked to aging, with further reduced connectivity as white matter begins to degenerate. This is an age when people face an increased risk of developing various health problems that can affect the brain, such as hypertension.”
83 years old – Late aging
The final turning point occurs around the age of 83. Data on this latter era are more limited, but the defining characteristic is the shift from global to local. Whole-brain connectivity declines further and becomes dependent on certain regions while others fade.
“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 eras,” added study co-author and neuroscientist Duncan Astle. “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 our brain’s structural journey is typically one of a few major turning points instead of a steady progression can help neuroscientists better identify when and how wiring is most vulnerable.
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