New research reveals the non-linear development of the human brain over its lifetime, identifying five major stages. Among the findings is the conclusion that “adolescence” in brain development lasts far longer than previously thought
Published in the journal Nature Communications, and reported in Neuroscience News, the study maps out the brains’ topological turning points using brain scans from over 3,800 individuals ranging in age from less than a year old to 90. Rather than a steady progression throughout our lives, the data showed our brains experience non-linear change.
Researchers at the University of Cambridge’s MRC Cognition and Brain Sciences Unit were able to identify four major topographical turning points across a lifetime – around 9, 32, 66 and 83 years old – that define the five major epochs of topological development, each with distinctive age-related changes.
“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,” Dr Alexa Mousley, a Gates Cambridge Scholar who led the research, told Neuroscience News. “This study is the first to identify major phases of brain wiring across a human lifespan.”
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The first epoch (ages 0 to 9) sees white and grey matter volume increase rapidly even as the overabundance of connectors between neurons created during infancy are pruned back through synaptic elimination, leaving behind the most active ones.
The brain experiences a step-change in cognitive capacity at the first turning point, as well as an increased risk of mental health disorders as it transitions into the second epoch (9 to 32). White matter continues to grow during this adolescence era, increasingly refining the organisation of the brain’s communications networks and marks the only increase in neural efficiency.
That efficiency peaked in the early 30s, when researchers saw “the most directional changes in wiring and largest overall shift in trajectory” of any turning point. Then the brain enters adulthood (32 to 66), remaining largely stable even as those communication networks reorganise and white matter begins to degenerate, culminating in the mid-60s with the turning point into early ageing (66 to 83).
While data for the last epoch is limited, it is defined by further compartmentalisation and increased reliance on certain regions.
“These eras provide important context for what our brains might be best at, or more vulnerable to, at different stages of our lives,” Mousley explained. “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.”
