Teaching, neuroscience and the teenage brain.

There is a great deal of debate at the moment about neuroscience and its potential within educational settings. The Association of Teachers and Lectures (ATL) have even debated the possibility that neuroscience should become part of teacherTeenBrain training, partly inspired by the recent interest teachers have shown towards evidence based teaching and learning. Some of the most fascinating research to come from neuroscience over the past few years has been from neuroscientists and cognitive psychologists like Sarah-Jayne Blakemore and her colleagues at University College London. Blakemore and her team have spent a great deal of time looking at the way the teenage brain develops in comparison to the brains of younger children and adults. They use a technique known as Magnetic Resonance Imaging (or MRI) in order to examine the inner workings of the living human brain. Before the introduction of MRI the only way psychologists and neuroscientists could investigate brains without surgery was through post-mortems of the recently deceased so the main advantage of MRI is that researchers can now study living brains while they are in the process of remembering, deliberating and making decisions. It was generally considered that the crucial period for brain development was the first three years of life and, certainly, there are many major changes taking place during this period, changes that include the growth of specialist cells known as neurons.

Astonishingly the adult human brain contains about 80 to 100 billion neurons (just as interesting is that the brain at birth contains only slightly less) but these neurons are only part of a much bigger story. Even before birth the majority of the critically important aspects of the brain are already in place, having begun to develop during the first week of gestation. By the seventh month of gestation pretty much all of the neurons that will make up the mature brain have already been formed. The most significant transformation during the early years of life is not the neurons themselves but rather the wiring of connections between them, known as synapses. The synapse is the way in which neurons communicate with each other in the form of electrical impulses or through special chemicals known as neurotransmitters. These neurotransmitters can have a major impact on our behaviour and emotional state, for example, low levels of the neurotransmitter serotonin has been linked to depression, which is why anti-depressants known as Selective Serotonin Re-uptake Inhibitors (or SSRI’s) like Prozac, have proved highly successful in the treatment of depression and related conditions. The neurotransmitter dopamine has been linked to other psychological disorders including schizophrenia; anti-psychotic drugs help to regulate these levels and appear to successfully treat the symptoms related to such conditions. Neurons don’t touch each other so information (electrical or chemical) is released by one neuron and received by another via a gap known as the synaptic cleft (this process is known as synapses). As we learn new things, be it reading, writing or riding a bike, a new connection between neurons is made and the more often the activity is carried out the stronger the connection becomes. This is why the more we repeat a procedure the easier it becomes to do so that, in same cases such a driving the car to work and back each day, our actions become so automatic that we often forget having carried them out.

This increase in connections during the early years of life is called synaptogenesis and can last for several months depending on the species of animal. Astonishingly, the number of connection in the young brain is so vast that synaptogenesis is followed by a period where many unused connections are eliminated through a process known as cognitive pruning which continues for a number of years. Once the process is complete the density of the connections will have reached adult levels. Studies conducted on monkeys have found that such density declines to adult levels at around three years, the point at which the monkeys reach sexual maturity.

Of course, monkeys aren’t humans and it would be highly erroneous to suggest that the development of a human infant mirrors that of other primates. Because the monkey develops faster, reaching sexually maturity at around three years of age, we must assume that the human infant develops somewhat more slowly. This view is astonishingly recent and prior to this it was assumed that humans, like monkey’s had reached maturity in terms of brain structure in early infancy. Unfortunately this error led to the view that infants reach a critical stage in development, after which they might not be able to learn certain skills vital to human growth such as language learning. A more probable situation is that infants pass through a sensitive period where certain aspects of learning are easier to achieve. Studies of feral children, those children who spend the first few years of life raised in the absence of human contact, have discovered that even if they fail to master language in early infancy, this skills can be obtained later in life – albeit with extreme difficulty. In fact, rather than brain development reaching full term in early childhood, Blakemore has discovered that teenage brains are still developing; it’s just that development is only taking place in certain brain regions. This has actually been known since the 1960’s but it is only now that researchers have access to fMRI scanners that they can support these views with evidence. The human brain matures at different rates; for example, the visual cortex should be in place by about ten months. After about this time synaptic density declines (unused connections are cut away through cognitive pruning), reaching adult levels by about ten years old. However, development of the frontal cortex appears to last well into the teenage years and the pruning process in much slower. In fact, synaptic density doesn’t peak until about the age of eleven years and the pruning process continues into the early twenties. This late stage of brain development may go some way to explaining teen behaviour but, before we get excited, there is a great many other factors to take into consideration.

Essentially, there appears to be two major changes that occur before and after puberty. During this period the actual volume of the brain tissue appears to remain stable, however, there is a significant increase in the amount of white matter in the frontal cortex of the brain. As already explained, neurons are continuing to develop and new connections are being formed during this period. The neurons themselves are busy building up a layer of a fatty tissue called myelin on the axon of the cell. The axon is responsible from carrying electrical impulses away from the cell body of the neuron, down the shaft of the axon toward the dendrites, causing one cell to communicate with another. Myelin acts as an insulator and increases the speed of the electrical transmission between the neurons (so it might be related to intelligence – hence the omega 3 hype from a few years back). The fatty tissue of the myelin shows up white under a microscope (hence white matter) and would suggest that the speed at which they communicate with each other significantly increased after puberty. The second major change was first identified by Peter Huttenlocher of the University of Chicago. Brain development in the brains of children leads to a major increase in connections (synaptogenesis) in pre-pubescence followed by major decrease in the density of synapses after puberty. This appears to support other studies that have concluded that while unused connections are pruned; those that are used are strengthened. This appears to suggest that teenagers (and only teenagers) go through a process of brain fine-tuning in the frontal cortex throughput the teenage years.

The frontal cortex (literally the part of the brain at the front of the skull) is the home of what cognitive psychologists and neuroscientists call executive functions. These executive functions are involved in a number of activities including our ability to anticipate the consequences of our own actions, our capacity to decide between good and bad actions and the ability to suppress unacceptable unsocial behaviour. It is also concerned with what is known as social cognition – the way in which we co-operate and communicate with others so that we can successfully exist with members of our own species. The frontal cortex also allows us to modify our emotions so that they can fit within socially accepted norms. Could this later stage of brain development explain why some teenagers can become so difficult during this period of rapid and complex change? American Psychologist, Mike Bradley seems to think so. Bradley has even gone so far as to suggest that adolescence is a form of mental illness caused by the immature yet rapidly developing state of the teenage brain. While many would pour scorn on Bradley’s suggestion, it does appear that something is occurring in the teenage brain that compels them to behave in a certain manner, a manner that many adults might view as unacceptable.

So what does all this really mean to parents, teachers and other adults who work with teenagers? The research is all well and good but unless it can help us to help teenagers (or at least begin to appreciate the huge changes taking place within the context of educating children) knowing what is happening in the brains of our teens is of little use. Additionally, many neuroscientists are still unsure of how their discoveries can impact on education and learning. Blakemore’s research would suggest that teaching teenagers is even more complex than we currently believe because of the way the brain is continuing to develop and its impact on executive functioning. This doesn’t mean that we should reject neuroscience (I was completely taken with Blakemore’s research when I first read it a few years ago and became even more so when I attended her talks) but it does suggest caution.

Blakemore would herself admit that there is a great deal of uncertainly about how we can use this research to inform teaching practice – but that doesn’t mean we shouldn’t at least investigate some of the possibilities.


2 thoughts on “Teaching, neuroscience and the teenage brain.

  1. Pingback: Of flaws and flows | teaching personally

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