The magic of myelin

The loft in my house is heavily insulated with a yellow material made of glass fibre. Every time I open the hatch to retrieve a suitcase or box of toys, I’m showered with thick strands of the stuff. Not only do I look ridiculous in a frizzy yellow wig, but – because glass fibre is an irritant – I also itch for hours afterwards. You’d assume, therefore, that I disliked insulation. But you’d be wrong…

You see, insulation holds the key to developing and perfecting skills.

Practice makes permanent

Our brains are like the back of an electrician’s van: a tangle of coloured wires – about 100 billion to be imprecise. These wires are called neurones and they are connected to each other by synapses. Whenever we do something – think, move, read this article – our brain sends a signal down these neurones to our muscles.

In other words, every skill we possess – swinging a golf club, writing great fiction, playing the piano – is created by chains of nerve fibres carrying small electrical impulses like the signals travelling through a circuit.

Each time we practise something, a different highly specific circuit is illuminated in our heads like fairy lights strung round a Christmas tree. It is these circuits, not our muscles, that control our thoughts and movements. Indeed, the circuit is the movement because it dictates the content of each thought and the timing and strength of each muscle contraction.

More importantly, each time we practise something – be it a mental or physical skill – our nerve fibres are coated in a layer of insulation called myelin which acts in much the same way as the rubber insulation that coats a copper wire or that horrible yellow stuff in my loft: it makes the electrical impulses stronger and faster by preventing the signals from leaking.

Each time we practise a skill, a new layer of myelin is added to the neurone like the lagging on a boiler. The thicker the myelin gets, the better it insulates our nerve fibres and, therefore, the faster our movements and thoughts become.

But that’s not all. As well as getter faster, our thoughts and movements also become more accurate as we add more and more layers of myelin. Why? Because myelin regulates the velocity with which those electrical impulses travel through our nerve fibres, speeding up or slowing down the signals so that they hit our synapses at exactly the right moment. And timing is all important because neurones are binary: either they fire or they don’t. Whether or not they fire is dependent on whether the incoming impulse is big enough to exceed their so-called “threshold of activation”.

Imagine, for example, a skill circuit where two neurones have to combine – doubling their impulses – to make a third high-threshold neurone fire, for example, to serve an ace in a game of tennis. In order to combine their forces effectively, the two incoming impulses must arrive at almost exactly the same time (and by “almost”, I mean within about four milliseconds of each other). If the first two signals arrive more than four milliseconds apart, the third neurone won’t fire and the tennis ball will be called out.

Left to their own devices, because our brain has so many connections, our genes are unable to code our neurones to time things as accurately as this. That’s why we coat our nerve fibres with layers of insulation called myelin to help us achieve such precision.

The universal

If you are feeling somewhat dubious that myelin can hold to key to developing every imaginable human skill – from playing sports to playing Schubert – then remember this: everything on Earth is made from the same stuff – atoms. We may not closely resemble a fish or a tree, but we are all made from the same material and share the same cellular mechanism to convert food into energy.

Myelin is also universal: everyone can grow it, most swiftly during childhood but also throughout life. And it is indiscriminate: its growth enables the development of all manner of skills, both mental and physical.

In short, although skills vary in every which way – learning to play tennis is as different from learning to sing as learning to sing is from learning to write poetry – they all, without exception, rely on us growing more layers of myelin around our neurones which, in turn, relies on us practising over and over and over again.

Every skill is improved and perfected by performing it repeatedly because this helps us improve by honing our neural circuitry. And yet not all forms of practice are equal. We create myelin most effectively when we engage in deliberate practice, which is sometimes called deep practice.

Deep practice

Deliberate or deep practice is about struggling in certain targeted ways – placing artificial barriers in the way of our success in order to make it harder to learn something. In other words, you slow your learning down and force yourself to make mistakes.

This is what Robert Bjork calls “desirable difficulties”. By slowing down and making mistakes – by creating desirable difficulties – we ensure that we are operating at the edges of our ability. So the best form of practice – and therefore the best way to create more myelin – is to set yourself a target just beyond your current ability but within your reach.

This is where Vygotsky and his “zone of proximal development” comes in handy…

My loose interpretation of Vygotsky is this: we should perform tasks that are challenging but attainable. If the task is beyond our present ability then we will give up easily and learn nothing; if the task is too easy we will perform it out of habit without trying and will again learn nothing.

But if the task is hard yet just within our grasp, then we will learn. And because we struggle but overcome the challenge, our brains are rewarded with a dose of the naturally occurring chemical dopamine which makes us feel good and encourages us to keep on learning.

In The Talent Code, Daniel Coyle provides a useful example of deep practice. He presents two lists of word pairs as follows:



If we are given the first list to memorise in, say, a minute, on average we are likely to remember seven of the pairs.

But if we are given the second list we are likely to remember more than seven pairs because we have placed an artificial barrier in the way of our learning.

Because we have to fill in the missing letters, although this may take but a microsecond, we have to stop and stumble until we work it out. That microsecond, Coyle argues, makes all the different – in that moment, we don’t practise any harder but we do practise deeper. We slow down and locate what Robert Bjork calls “the sweet spot”.

This spot is the “optimal gap between what (we) know and what (we’re) trying to do (and) when (we) find that sweet spot, learning takes off”.

Let’s return to myelin, our magic insulation. Deliberate practice, deep practice or desirable difficulties – whatever you wish to call it – is the notion that targeted, mistake-focused practice is the most effective means of developing skills.

And it is quite so effective because the best way to build a fast and accurate neural circuit is – to quote Coyle – “to fire it, attend to mistakes, then fire it again, over and over”. Why? Because “struggle is not an option, it’s a biological requirement”.

The second key ingredient to skills development – after deep practice – is passion. You see, to be passionate about developing a skill is crucial because without passion you don’t have the determination or the persistence needed in order to dedicate the vast amounts of time and energy that are required of you to practice deeply. If you are not passionate, you don’t work hard enough and therefore you don’t create myelin.

In summary, and to quote Daniel Coyle again, practice does not make perfect, instead “practice makes myelin, and myelin makes perfect”. And, as we have seen, myelin operates by a few fundamental principles…

First, myelin is not built to respond to fond wishes or vague ideas; it is built to respond to actions – the electrical impulses travelling down nerve fibres. It responds to urgent repetition.

Second, myelin is universal in that it works on all skills. Regardless of its use, it grows according to the same rules.

Third, myelin wraps but it doesn’t unwrap. Once a skill circuit is insulated, it can’t be uninsulated except through age or disease.

Finally, although we retain the ability to create myelin all our lives, age has an effect. As children, myelin arrives in a series of waves, some of them determined by genes, some dependent on activity.

These waves last into our 30s, creating critical periods during which time the brain is extraordinarily receptive to learning new skills. We continue to experience a net gain of myelin until the age of 50 but at that point the balance tips toward a net loss.

The next time you venture into the loft, take a moment to admire the effects of insulation. When put to use in your house, it traps heat in and saves you money on your energy bill. When put to use in your brain, it traps electrical impulses and makes you perform every human skill faster and more accurately. And the insulation in your brain, unlike that in your loft, is free – you can make as much of it as you want so long as you’re willing to practice and practice.

Follow me on Twitter: @mj_bromley


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