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The Growing Brain
Published in the Times Educational Supplement, 2007
‘However old we are, our brain changes every day – the human brain has great plasticity,’ says neuroscientist Sarah-Jayne Blakemore of the Department for Cognitive Neuroscience at University College London, ‘Each time we recognise a new face, learn a new word, we make changes in our brain structure. In a changing environment, the normal brain can’t help but learn.’ So in her book The Learning Brain, written with Professor Uta Frith, Dr Blakemore reviews the latest neuroscientific findings on how that ‘natural’ learning can be shaped. Can education make better brains?
The emphatic conclusion is that it can. When teachers pass on the knowledge accrued by past generations, they help create enriched neural networks in their pupils’ brains. In teaching a child to read, for instance, we profoundly alter the architecture of that child’s brain, vastly increasing the interconnectivity between the nerve cells. And where there are problems in a growing brain, such as dyslexia or ADHD, the good teacher can help ameliorate them. ‘Education is to the brain,’ conclude Blakemore and Frith, ‘what gardening is to a landscape’.
The contents of the human skull do, of course, constitute quite a significant landscape. A baby is born with around a hundred billion nerve cells and, by the time that baby’s reached adulthood, about a hundred trillion interconnections have been forged between those nerve cells – an unimaginable network of learning. And we continue to make these connections throughout life.
To a large extent the direction of this growth is determined by the DNA of the cells that fused to create the baby in the first place – but from the moment of conception, it’s also influenced by the environment in which the brain grows. We may have a ‘language instinct’, for instance, but the language we end up speaking is determined by the language we’re exposed to in childhood. Nature and nurture are thus vibrantly interrelated.
‘Most research points to influences being about fifty-fifty genetic and environmental,’ says Dr Blakemore. ‘You can see it in developmental disorders like autism, dyslexia or ADHD. These are genetic or biological in origin, but environmental factors obviously interact to affect the way the child develops.’ In their book, she and Uta Frith, a leading world expert on autism and dyslexia, explain developmental disorders through a powerful image. They describe a number of automatic ‘start-up mechanisms’ in the brain, kicking in at certain predetermined points in a learner’s life to enable fast-track learning in various domains such as language or number. A specific learning disorder occurs when a particular module fails to start up, possibly also stopping others from developing too – like one domino that fails to fall, thus leaving a whole chain untoppled.
However, they point out that there’s also a ‘general learning system’ in the brain that can take over if a start-up doesn’t happen. It’s not as quick or efficient, but – given expert cultivation by a gifted gardener – most brains can compensate to some extent for developmental problems. Experience suggests this is best achieved by ‘patient and slow repetition of foundational elements that are normally taken for granted, and by providing explicit rules’ – a recipe which will be familiar to Special Needs teachers everywhere.
So the more neuroscience can tell us about the way brains function, the better equipped teachers at all stages in the educational system should be to tend their pupils’ cognitive landscape. Indeed, The Learning Brain looks forward to a ‘new science of learning’, an interdisciplinary science informed by neurophysiology, psychology and education.
Sarah-Jayne Blakemore emphasises that this learning must be seen as a life-long process. There are certain ‘critical periods’ of growth (although neuroscientists now prefer to call them ‘sensitive periods’, which has a less scary ring to it) when there’s a massive increase in the number of interconnections between brain cells, followed by a period of ‘pruning’ – which can be seen as fine-tuning the brain to the learner’s needs. However – as outlined above – even if something goes awry during these times, good teaching can help compensate.
Dr Blakemore had the opportunity to investigate one of these sensitive periods – early infancy – six years ago when seconded to the Houses of Parliament to compile a report on the most appropriate educational provision for young children. Neuroscientific findings in the 1990s had led to a craze in the USA for hot-housing young children – ‘enriching’ their experiences to provide more data for the brain cells to work on. But a review of the research led her to reject this idea. ‘After reviewing all the evidence, I concluded that, while deprivation is certainly bad for the brain, hyper-enrichment isn’t necessarily good for it. There’s no evidence that hot-housing is beneficial to brain development. It may even be damaging, but there’s no evidence yet one way or the other.’ She also points to lack of hard evidence about the currently hot topic of when children should begin formal learning of literacy skills. However, since she’s considering keeping her own summer-born son back a year so that he starts school at five rather than four, she clearly has her suspicions…
In recent years, Dr Blakemore has turned her attention to another possible sensitive period of brain development – adolescence. But while the proliferation and pruning of brain cell connections in infancy is very general (encompassing most areas of the brain), the changes in the adolescent brain are specifically associated with regions of the cortex, including the prefrontal cortex. This is the area of the brain that deals with the higher order activities of planning, self-awareness, selecting behaviour, and certain types of memory – sometimes referred to as ‘executive functions’. The prefrontal cortex is the most recent part of the human brain to evolve, so it’s not surprising that its internal wiring seems to take longer than more ancient areas.
Not only is there a dramatic reorganisation of connections related to the executive functions during this period, but there’s also a significant increase in ‘myelination’. Myelin is a white sheath of fat and protein that gradually develops around transmitter cells, insulating them and increasing the speed of interconnectivity. ‘Myelination goes on into your twenties,’ explains Dr Blakemore, ‘and it massively increases the speed of transmission between cells – the connections happen up to a hundred times faster.’
These changes imply that there should be an improvement during the teens and early twenties in an individual’s ability to focus attention, make decisions, exercise self-control and manipulate working memory to carry out more than one task at a time. There are also likely to be subtle but significant developments in awareness both of oneself and of others, including the ability to take on another person’s viewpoint – although these changes in social cognition may be temporarily obscured or confused by the effects of hormonal changes during puberty.
It’s clear therefore that the brain continues to grow and change over at least the first twenty years of life, and teaching methods at different stages in the educational process should, of course, be sensitive to these changes. The younger the learner, the more brain development is general – many areas of the brain are malleable in infancy, and require careful tending. As students reach adolescence, neural connections in most areas should be well established, but those in the regions associated with the executive functions continue to be fragile and malleable.
It would seem to make sense therefore, for primary teachers to concentrate on a more general, holistic approach to education, thus helping establish the overall architecture of the brain. They should also take into account that their pupils’ attention span is likely to be shorter than adults’, decision-making more difficult, and working memory less efficient. As Sarah-Jayne Blakemore puts it: 'Some tasks that seem negligible to adults are in fact quite taxing for children.'
During the secondary years, teachers should be able to assume that overall interconnectivity is established, and concentrate on the still fragile areas in the prefrontal cortex, helping their students become steadily more capable of selective attention, decision-making, planning and multi-tasking.
But as well as cultivating the cerebral landscape, teachers also need to be aware of other, potentially harmful, environmental influences that could undermine their work. Susan Greenfield, the President of the Royal Institution, recently drew attention to the possible adverse effects of too much screen-based activity on developing brains. In the same week, a new study from the Institute of Psychiatry suggested cannabis use in adolescence can also be seriously damaging. ‘It seems cannabis can be a profound environmental factor during this sensitive period of brain development,’ says Dr Blakemore. ‘Perhaps it leads to over-pruning of the connections between the cells, perhaps it inhibits pruning… we don’t know yet. But this study puts it beyond doubt that cannabis use in adolescence is associated with an increasingly high risk of schizophrenia among young people. It’s clearly affecting the development of their brains.’
Cultivating brains
If education is to the brain what gardening is to a landscape, the gardeners need to be aware of certain key features of the terrain.
- Brains are highly plastic – the remarkable plasticity of the brain means that learning is always possible. Even when things go wrong neurologically or environmentally, the right sort of teaching – appropriate to the particular learner concerned – should be able to compensate to some extent for all but the most profound disability or deprivation.
- Brains develop over time – the neural networks in the brain go through several waves of proliferation and pruning during childhood and adolescence (and it’s possible there may be even further fine-tuning in adulthood). These periods of fine-tuning make the brain less flexible but more efficient. Myelination – the development of insulating white matter around transmitter cells which speeds up interconnectivity – also develops over time. Teaching should be sensitive to learners’ specific stage of development – it’s possible that inappropriate experiences (such as rushing learners to achieve before they’re sufficiently mature) might actually inhibit effective learning.
- Brains are influenced by environmental factors – the dramatic reorganisations of the brain described above result from genetic programming, but are also affected by environmental factors. In the words of the eminent neuroscientist Susan Greenfield, ‘the human brain is exquisitely sensitive to any and every event. We cannot complacently take it as an article of faith that it will remain inviolate, and that consequently human nature and ways of learning and thinking will remain constant.’ It’s important that teachers – like good gardeners -- are aware of all the possible environmental factors affecting the cognitive terrain, so they can help learners avoid potentially damaging influences.