The brain evolves through five dramatic wiring eras that shape how we think, grow, and age.
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The human brain appears to move through five distinct structural eras, each separated by major turning points from birth to old age.
Researchers found that the brain moves through five major eras of wiring, shaped by four pivotal turning points that typically occur around ages nine, 32, 66, and 83.
Brain development that we usually think of as “adolescent” actually continues far longer than expected, often lasting into the early thirties before the mature adult pattern of neural wiring finally takes hold.
Brain development that we usually think of as “adolescent” actually continues far longer than expected, often lasting into the early thirties before the mature adult pattern of neural wiring finally takes hold.
Five Epochs of Lifespan Brain Architecture Identified
Neuroscientists at the University of Cambridge have outlined five major “epochs” that describe how the brain’s structure evolves from birth to old age. These stages reflect large-scale reorganizations in the brain’s wiring that support new ways of thinking as people develop, mature, and eventually experience decline.
A research team from Cambridge’s MRC Cognition and Brain Sciences Unit analyzed MRI diffusion scan data from 3,802 individuals ranging from newborns to 90 years old. These scans track the movement of water through brain tissue, allowing scientists to map the pathways that link different regions.
Published today (November 25) in Nature Communications, the study reports that human brain structure tends to move through five broad periods over a lifetime. Four major “turning points” divide these phases, marking ages when the brain’s network layout shifts in notable ways.
All Eras: representative MRI tractography images of all eras of the human brain.
Credit: Dr. Alexa Mousley, University of Cambridge
Childhood, Adolescence, and the First Major Shifts
The first period of brain topology extends from birth to approximately age nine. This is when the transition into the adolescent phase begins, a period that continues until about age 32 on average.
During the early thirties, the brain’s wiring pattern moves into what the researchers describe as the adult mode. This adult period is the longest, lasting more than 30 years. A subsequent turning point around age 66 marks the beginning of an “early aging” phase, followed by a “late aging” period emerging near age 83.
“We know the brain’s wiring is crucial to our development, but we lack a big picture of how it changes across our lives and why,” said Dr. Alexa Mousley, a Gates Cambridge Scholar who led the research. “This study is the first to identify major phases of brain wiring across a human lifespan.”
“These eras provide important context for what our brains might be best at, or 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 it be learning difficulties in childhood, or dementia in our later years.”
Credit: Dr. Alexa Mousley, University of Cambridge
How the Brain Changes from Infancy to Age Nine
From birth through childhood, the brain is shaped by a process known as “network consolidation.” Infants produce an enormous number of synapses, the links between neurons. Over time, only the most active connections remain while the rest are trimmed away.
Across this entire period, the brain follows a consistent pattern of rewiring. Grey and white matter grow quickly, which causes cortical thickness (the distance between outer grey matter and inner white matter) to reach its highest point. The folds of the outer cortex also stabilize during this time.
By age nine, the brain encounters its first major turning point. Cognitive abilities expand significantly, but the risk of mental health conditions also becomes more pronounced.
How the Brain Changes from Infancy to Age Nine
From birth through childhood, the brain is shaped by a process known as “network consolidation.” Infants produce an enormous number of synapses, the links between neurons. Over time, only the most active connections remain while the rest are trimmed away.
Across this entire period, the brain follows a consistent pattern of rewiring. Grey and white matter grow quickly, which causes cortical thickness (the distance between outer grey matter and inner white matter) to reach its highest point. The folds of the outer cortex also stabilize during this time.
By age nine, the brain encounters its first major turning point. Cognitive abilities expand significantly, but the risk of mental health conditions also becomes more pronounced.
Credit: Dr. Alexa Mousley, University of Cambridge
Adolescence: Increasing Neural Efficiency and Network Refinement
In the second epoch, the adolescent brain continues to build white matter volume, allowing communication networks to become more organized. Diffusion scans show that water movement through these pathways becomes increasingly structured, reflecting a more streamlined system.
This period is defined by improving efficiency within individual brain regions and faster coordination across the entire brain. These changes support stronger cognitive performance.
“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,” said Mousley.
Adolescence: Increasing Neural Efficiency and Network Refinement
In the second epoch, the adolescent brain continues to build white matter volume, allowing communication networks to become more organized. Diffusion scans show that water movement through these pathways becomes increasingly structured, reflecting a more streamlined system.
This period is defined by improving efficiency within individual brain regions and faster coordination across the entire brain. These changes support stronger cognitive performance.
“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,” said Mousley.
Credit: Dr. Alexa Mousley, University of Cambridge
These refinements reach their peak in the early thirties, which scientists describe as the “strongest topological turning point” of the lifespan.
“Around the age of 32, we see the most directional changes in wiring and largest overall shift in trajectory, compared to all the other turning points,” said Mousley.
“While puberty offers a clear start, the end of adolescence is much harder to pin down scientifically. Based purely on neural architecture, we found that adolescent-like changes in brain structure end around the early thirties.”
These refinements reach their peak in the early thirties, which scientists describe as the “strongest topological turning point” of the lifespan.
“Around the age of 32, we see the most directional changes in wiring and largest overall shift in trajectory, compared to all the other turning points,” said Mousley.
“While puberty offers a clear start, the end of adolescence is much harder to pin down scientifically. Based purely on neural architecture, we found that adolescent-like changes in brain structure end around the early thirties.”
Credit: Dr. Alexa Mousley, University of Cambridge
Adulthood: Stability and Slow Compartmentalization
At about age 32, the adult epoch begins. Compared with earlier phases, the brain’s architecture becomes more stable, and there are no major turning points for roughly three decades. According to other studies noted by the team, this period aligns with a “plateau in intelligence and personality.”
Researchers also observed growing “segregation” during adulthood, meaning brain regions gradually become more specialized and separate in their functions.
The turning point near age 66 is relatively subtle. Although it does not involve a dramatic restructuring, the team still detected meaningful shifts in the arrangement of brain networks.
“The data suggest that a gradual reorganization of brain networks culminates in the mid-sixties,” said Mousley. “This is probably related to aging, with further reduced connectivity as white matter starts to degenerate.
“This is an age when people face increased risk for a variety of health conditions that can affect the brain, such as hypertension.”
Late Aging: Declining Global Connectivity
The final major turning point occurs around age 83. After this, the brain moves into the last epoch of structural organization. Although less data is available for this stage, researchers found that the brain shifts from broad, global connectivity to a pattern that relies more heavily on certain regions as overall communication weakens.
“Looking back, many of us feel our lives have been characterized by different phases. It turns out that brains also go through these eras,” added senior author Prof Duncan Astle, Professor of Neuroinformatics at Cambridge.
“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 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.”
Adulthood: Stability and Slow Compartmentalization
At about age 32, the adult epoch begins. Compared with earlier phases, the brain’s architecture becomes more stable, and there are no major turning points for roughly three decades. According to other studies noted by the team, this period aligns with a “plateau in intelligence and personality.”
Researchers also observed growing “segregation” during adulthood, meaning brain regions gradually become more specialized and separate in their functions.
The turning point near age 66 is relatively subtle. Although it does not involve a dramatic restructuring, the team still detected meaningful shifts in the arrangement of brain networks.
“The data suggest that a gradual reorganization of brain networks culminates in the mid-sixties,” said Mousley. “This is probably related to aging, with further reduced connectivity as white matter starts to degenerate.
“This is an age when people face increased risk for a variety of health conditions that can affect the brain, such as hypertension.”
A representative MRI tractography image of the fifth era of the human brain. This image is representative of the general pattern seen across the brains in the study during the fifth era of neural wiring, the the “late aging” phase.
Credit: Dr. Alexa Mousley, University of Cambridge
Late Aging: Declining Global Connectivity
The final major turning point occurs around age 83. After this, the brain moves into the last epoch of structural organization. Although less data is available for this stage, researchers found that the brain shifts from broad, global connectivity to a pattern that relies more heavily on certain regions as overall communication weakens.
“Looking back, many of us feel our lives have been characterized by different phases. It turns out that brains also go through these eras,” added senior author Prof Duncan Astle, Professor of Neuroinformatics at Cambridge.
“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 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.”
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