New Research Uncovers the Five Eras of the Human Brain
Q&A with Professor Duncan Astle
Robinson Fellow, Professor Duncan Astle (pictured left), Deputy Director of the MRC Cognition and Brain Sciences Unit, is helping to reshape how we understand the human brain. Drawing on brain scans from nearly 4,000 individuals, his research – led jointly with Dr Alexa Mousley - identifies five distinct “eras” of brain development—from childhood through to late ageing:
1. Childhood – from birth to age nine
2. Adolescence – from nine to 32 years old
3. Adulthood – from age 32 to 66
4. Early ageing – from 66 to 83 years old
5. Late ageing – from 83 onwards
Rather than a smooth, gradual process, these findings suggest that our brains evolve in stages, each with its own strengths, vulnerabilities, and patterns of neural wiring.
Q: What first motivated you to investigate whether the brain develops in distinct “eras”?
A: The way we study the human brain is undergoing a major revolution. One key ingredient is the size of the datasets available – we worked with collaborators to amass a dataset of over 4,000 brain scans that cover the entire human lifespan. The second key ingredient is the computing power needed to build models about how brain organisation changes. These two big changes in our field inspired us to think about asking this question about “eras” and “turning points”. Until about five years ago, it was simply not possible.
Q: The idea that, aged nine, childhood ends and adolescence begins and then extends into our early 30s challenges common assumptions. How might this inform how we approach major life milestones?
A: In cultures across the globe we assign different ages to adulthood. We can serve in the Armed Forces from 16, drive from 17, drink from 18. But there is nothing special about these ages. As far as our brains are concerned they do not reach a stable adult plateau until our early 30s. In fact, many major life milestones – such as starting a family – now align with this model.
My own feeling is that we should regard our 20s as an extended adolescence, and indeed many of us make big changes when adulthood finally does arrive.
Q: To what extent can life experiences—like education, stress, or parenthood—shape or shift these brain phases?
A: The phases are universal. But different phases of life are differentially sensitive to experiences like stress. We already know that there are sensitive or critical windows. These can cut both ways. For instance, in the first epoch of life we need vital linguistic and social inputs. If those are missed, then we cannot recover those functions. Conversely, experiencing stress can have a very negative impact depending upon which phase of life we are in.
Put simply, whilst there are certainly innate predispositions, the way that our brains organise in different phases of life is heavily impacted by environment and experience. But the phases themselves are common to us all.
Q: Could this framework of “brain eras” eventually be used in clinical settings or have other benefits in how we support cognitive health?
A: I honestly think it already is. For instance, we already know that adolescence is an extended period of vulnerability for mental illness - 75% of all mental illness will have its first onset before we’re 25 years old.
What this study shows is that the brain is constantly reorganising itself across the entire life-span. It may well be that a whole host of different conditions can be situated within these newly defined epochs of life.
Q: How might this research evolve with advances in AI or neuroimaging technologies?
A: We are already there. This study was only possible because of population-level neuroimaging - data sharing at a scale previously unseen. Information gathered was combined using a branch of artificial intelligence called machine learning. Interestingly, this is increasingly becoming a two-way street. Things we’ve learnt about how the brain develops and organises are already being incorporated in the way artificial systems, even the chips themselves, are designed. And later this year we are launching the UK’s first Master’s course in exactly this space – the MPhil in NeuroAI and Intelligent Systems.
Q: What are the next big questions your team is hoping to answer?
A: We’re focusing very heavily on early development. In fact, we are currently running a study with 6-week-old babies. We are scanning their brains and taking blood samples to explore how the development of the immune and nervous systems are interlinked. Understanding these connections could help us determine how our genetic background shapes our likelihood of experiencing mental illness. In turn this could open the door to policy interventions or even targeted interventions that start much earlier in life.
Find out more about this fascinating research.