When Shakespeare sketched his Seven Ages of Man, he imagined the arc of a human life progressing from mewling infancy to a decrepit “second childishness”. Neuroscientists at the University of Cambridge have suggested he may have slightly overestimated. The brain goes through significant change at the ages of 9, 32, 66 and 83.
When it comes to the brain, research suggests there are actually five distinct ages — including an adolescent phase that extends into your thirties and a period of stable high performance that ends in your mid-sixties. Nudging 70 at peak performance, I completely agree!
Alexa Mousley, a Gates Cambridge Scholar who led the research, said: “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. This study is the first to identify major phases of brain wiring across a human lifespan.”
Her team analysed MRI scans from more than 3,800 people, ranging from infants to individuals in their nineties.
The results, published in Nature Communications, revealed four pivotal turning points — around the ages of 9, 32, 66 and 83 — that divide a human life into five “epochs” of brain structure.
During the first, from birth to about the age of nine, the connections between separate areas of the brain become less efficient. It takes more effort to send information between distant regions. If the brain were a city, its roads would be more convoluted, taking longer to travel from one neighbourhood to another.
However, within each neighbourhood, the brain is getting better at specialised tasks. Clusters of neurones start building stronger, tighter bonds — a process known as local segregation.
The first significant shift, at the age of nine, coincides with a surge in cognitive skills but also rising vulnerability to mental health disorders.
The connections linking separate regions start to work more effectively. Communication between disparate brain areas becomes much more efficient.
This period, which lasts until 32, has been described by the researchers as a surprisingly lengthy adolescent phase. It builds to a moment of peak performance, most commonly in a person’s early thirties.
Next comes a plateau, stretching from about 32 to 66, during which measures of intelligence and personality traits tend to remain stable.
The next structural shift, at about the age of 66 is marked by the start of a subtle deterioration in the brain’s white matter — the network of fibre-like cables that allow different regions to talk to each other.
The final turning point, at 83, ushers in a phase where different brain neighbourhoods become more isolated. Direct connections between regions break down. There’s an increased reliance on local networks — a neurological echo, perhaps, of Shakespeare’s “second childishness”.
Duncan Astle, a professor of neuroinformatics at Cambridge, who is senior author of the study, said:
“Looking back, many of us feel our lives have been characterised by different phases. It turns out that brains also go through these eras.
“Many neuro-developmental, 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 behaviours.”
He added:
“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.”
This limerick by Robert Conquest summarises the journey.
“Seven Ages: first puking and mewling
Then very pissed-off with your schooling
Then fucks, and then fights
Next judging chaps' rights
Then sitting in slippers: then drooling.”