Large MRI Study Maps Five Distinct Brain Epochs Across the Lifespan

A team of neuroscientists analyzed MRI scans from 3,802 neurotypical participants aged from infancy to 90 and identified four major turning points in brain wiring that divide life into five broad neurological epochs: childhood, adolescence, adulthood, early aging and late aging. The study tracked changes in network measures such as global efficiency (how well distant brain regions communicate) and modularity (how segregated functional networks are), revealing a clear, lifespan-wide pattern of growth, refinement, stabilization and decline.

How the researchers studied brain wiring

The team used structural MRI to quantify brain connectivity and computed graph-based network metrics across age. By examining changes in these measures from birth to age 90, they identified consistent inflection points near ages 9, 32, 66 and 83 that mark shifts in the brain's structural trajectory.

Five brain epochs

1. Childhood (0–9 years): The brain undergoes rapid expansion in both gray matter (neuronal cell bodies) and white matter (axonal wiring). This period is characterized by exuberant growth followed by synaptic pruning as networks reorganize for greater efficiency approaching puberty.

2. Adolescence (≈9–32 years): Hormonal changes and continued white-matter growth drive further refinement. Both local and global communication efficiency steadily improve as networks become more specialized.

3. Adulthood (≈32–66 years): Around age 32, structural change slows and the brain's architecture stabilizes. Over the following decades, brain regions become progressively more segregated and compartmentalized—an extended period of network reorganization rather than rapid growth or loss.

4. Early aging (≈66–83 years): Scans show the first clear signs of decline: networks become sparser, connection density drops, and overall efficiency decreases, likely reflecting age-related white-matter degeneration and other aging processes.

5. Late aging (≈83+ years): Whole-brain connectivity continues to fall and cognitive effort becomes more reliant on local networks. The researchers note the oldest group was smaller in number, so findings here warrant cautious interpretation and additional study.

Implications and caveats

These structural epochs provide a framework for understanding when the brain may be most adaptable or vulnerable—for example, why learning difficulties often emerge during development or why dementia risk increases in later life. The authors call for targeted studies in under-sampled phases (particularly older ages) and for investigations linking structural changes to function, behavior and health outcomes. Recent work linking menopause to measurable brain-structure shifts illustrates how life events can map onto these broader epochs.

Lead author Alexa Mousley and senior author Duncan Astle emphasize that while the study maps broad patterns of structural change, many questions remain about how these shifts translate into cognition and disease risk. The findings were published in Nature Communications.