Cellular Mechanisms of Learning

In a comment on a recent post, BusyB asked if I had read the book The Talent Code by Daniel Coyle.  I had not at the time, but quickly requested it from the good ol’ Vancouver Public Library.  The author has a pretty straightforward premise:  to get good at something, you have to engage in what he calls “deep practice”, and this increases your talent by causing the growth of myelin in your brain.

What do I think about this?  I’ll talk about talent and practice (and the inevitable nature-vs-nurture question) at a later date, but today I want to talk about what happens in our brain when we learn something.  Let me say right off that I find Coyle’s claim that skill-building equals myelin growth such a gross oversimplification that I literally cringed every time myelin was mentioned.  The book was peppered with repeated sentences such as “Skill is myelin insulation that wraps neural circuits”.  And, really?  It’s just not that simple.  Sorry.

Let me back up and tell you a little bit about neurons and synapses and myelin and what we think happens to them during learning.

Neurons in a nutshell

You probably know that neurons are brain cells, and you have billions of them in your head and spinal cord.  Neurons “talk” to one another electrically through specialized connections called synapses.  Here’s a schematic view of two neurons (one blue, the other green) connected by a couple of synapses.

The axon is the part of the neuron that carries electrical impulses away from the cell body.  At the end of the axon, there are specialized endings where the electrical signal gets transferred onto the dendrites of another neuron.  These are the synapses.  In most neurons, the axon is wrapped up in an electrical insulator made of a substance called myelin.  Electrical impulses travel faster down axons that are insulated, and so the presence and amount of myelin on an axon alters the neuron's ability to transmit electrical signals.

Learning makes stronger connections between neurons

That’s, in a very small nutshell, how neurons work.  And although I’ve only shown two neurons in my diagram, every neuron is connected to many, many other neurons, forming a complex spider’s web of neuronal circuits.  Almost everything that happens in our brains comes down to circuits of neurons transmitting electrical signals.  So when we learn something new, or get better at doing something, what happens in our brains is that the neuronal circuits responsible for that fact or skill become stronger, better able to communicate with one another. 

There are several main ways in which this can happen:

1)  The synapses themselves become stronger and so transmit the signals more reliably

2)  New synapses form, so the neurons are more strongly connected

3)  Myelin growth leads to faster transmission of the electrical signals down the axon, and better timing of neuronal signals.

The synaptic mechanisms (numbers 1 and 2 above) have been studied in excruciating detail (or at least that's how it feels to people like me who have spent years in nitty-gritty synaptic research) and scientists as a group are slowly getting a handle on how changes in synapses happen and how this helps us learn things. 

Neurons that fire together wire together

Here’s how scientists think that learning works:  The basic idea is that every thought is encoded by the firing of a specific group of neurons, all connected in a circuit.  So a particular circuit fires when we think of the note middle C, for example.  And there’s another circuit that fires when we picture a note on the first ledger line below the treble clef staff.  When we learn that this position on the staff corresponds to middle C, both of these circuits fire at the same time.  And when neurons fire at the same time, the connections between the neurons get stronger.  The synapses get stronger, and/or new synapses form.  This means that the next time we fire the circuit that means “note on the first ledger line below the staff”, the circuit that corresponds to “middle C” is more likely to fire.  Neuroscientists have a saying for this:  "Neurons that fire together wire together”.  From a learning standpoint, it means that we have learned to connect those two ideas by physically altering the way the neurons in our brain are connected.

These changes in synaptic strength very clearly happen when we learn something, whether new facts or new skills.  Synaptic changes are an important part of learning during development, and relearning following brain injury.  There is a ton of research showing this.  The fact that Coyle doesn’t even mention these types of mechanisms as taking place during learning is kind of ridiculous.

Myelin and Learning
So what about myelin?  Does myelin growth aid in skill learning, as Coyle purports?  The answer, based on scientific research, is “probably”.  There are correlational studies showing that people who are more skilled at certain tasks (like reading, or playing music) have greater myelination in areas of the brain related to those tasks.  In particular, musicians have a larger and more myelinated corpus callosum, the axon bundle that connects the two halves of the brains.  This is especially true for musicians who began their musical training before the age of 7, which makes sense, because the myelination of the nervous system is something that occurs throughout childhood and is not complete until a person is in their mid-twenties.  Myelination of neurons during learning in adults is still a controversial idea, and research in this area is on-going.  I’m interested in this line of research, especially the thought that the amount of myelin helps to co-ordinate the arrival of signals from different neurons.  Perhaps myelination plays a greater role in learning of skills compared to learning of facts (implicit vs. explicit learning), but I was not able to find any evidence for this in the scientific literature.

What do I think about The Talent Code?  I agree with the (rather obvious) idea that hard works leads to the acquisition of skills, but I think there are better and more interesting books that address this topic (this one, for example).  However, I think the scientific side of his book is weak, oversimplified and kind of misleading.

References

Bengtsson SL, Nagy Z, Skare S, Forsman L, Forssberg H, Ullen F. (2005) Extensive piano practicing has regionally specific effects on white matter development. Nat. Neurosci. 8(9):1148-1150.

Fields RD. (2008) White matter in learning, cognition and psychiatric disorders. Trends Neurosci. 31(7):361-370.

Schlaug G, Jäncke L, Huang Y, Staiger JF, Steinmetz H. (1995) Increased corpus callosum size in musicians. Neuropsychologia. 33(8):1047-1055.

Ullén F. (2009) Is activity regulation of late myelination a plastic mechanism in the human nervous system? Neuron Glia Biol. 5(1-2):29-34.

Musical Cognition

I’ve just finished reading Henkjan Honing’s Musical Cognition:  A Science of Listening.  Although I had low hopes for another book about how we process music, written for the layperson, I found it to be a little gem of a book, with bite-sized, digestible chapters. 

And many of the chapters did require a bit of chewing and digestion.  The book is indeed written for the layperson, eschewing jargon and complicated figures, but that does not mean that Honing assumes (as many authors seem to do) his reader to be uneducated or slow-witted.  On the contrary, Honing allows the reader space to consider and contemplate as he carefully but conversationally guides the reader through such knotty problems as “What is music” and “How do we recognize beat and meter in music?”, referring to his own research and that of others to describe approaches to answering these questions.  I admit that I didn’t always feel like thinking that hard, but it was well worth the effort.

In the end, one of main points of this book is that we are all trained listeners, with a lifetime of experience at listening to music.  The "illiterate" listener, lacking formal musical training, is almost as good at listening to and understanding music as a professional musician, but is not able to put names on all he hears.  What the illiterate listener lacks is mostly musical vocabulary.

Far from being the fluffy read I anticipated, this book was thoughtful and thought-provoking.  I’d love to sit down with Honing and discuss the questions raised in this book over several cups of coffee.

This is my Brain on Books about the Brain

Ahhhh… The kids are back at school and I finally have a little time to myself.  As I take a few days to catch up, I thought I’d give you an informal post about what neuroscience and music books I’ve been reading lately (and what I think about them), what I’m reading right now, and also what I plan to read soon.

I should preface my reviews of these books by saying that I generally have little patience for books written about music and the brain.  This sounds like I’m being snotty, but it’s just a topic that I already know a lot about, so I have to sift through a lot of information to find something that catches my interest.  Daniel Levitin’s bestseller This is Your Brain on Music was particularly mind-numbing for me (although I do recommend it), because it assumes the reader knows nothing about music and nothing about the brain.  It’s a good book, but I am certainly not the intended audience.

Anyway, I’ve recently finished two books “for the layman” about music and science:  Healing at the Speed of Sound, by Don Campbell and Alex Doman, and The Power of Music by Elena Mannes.  Although the two books cover very similar topics, they are very different.

When I read an interview with the Don Campbell on Salon.com, I immediately requested Healing at the Speed of Sound from the library.  The book purports to discuss how pervasive music has become in our society, especially through the use of ipods, and the effect that this is having on our brains.  Sounds interesting, no?  Unfortunately, the book did not live up to its potential.

I was a more than a little disappointed by the fluffiness of this book.  In part, it tries to be a self-help book, starting out with recommendations for music to start the day with.  Depending on how easy it is for you to wake up, the book recommends nature sounds, classical music, or rock ‘n’ roll.  And it goes on from there, discussing the whole soundtrack of your day.  Music to listen to in the car on the way to work, music to listen to at work.  Listen to Bach to increase your creativity, listen to driving rock while you work out to keep you energized.  You get the idea, I’m sure.  I was unimpressed. I can find my own playlists, thank you.

Later chapters read like an infomercial for the benefits of music.  This is not a story or a serious discussion, it’s more like a list of all the great things music can do for you.  Music is amazing!  Music can heal!  Music can make you smart!  There is very little detail about the research.  Although some of the claims the book makes are intriguing, I found that most of the references are newspaper or on-line new articles rather than original research or conversations with scientists, leaving me unsure what to believe.  Many of the topics are ones I am familiar with, so I have an idea of what research has been done, but the book didn’t offer me any of the caveats of the research, or tell me that some of the conclusions are only tentative.  And the repeated warnings throughout the book to turn down our music so as not to harm our ears left me feeling like this book was written by someone’s grandpa.  As my kids would say, “I know, that; I’m not a dumb-head!”

In contrast to Campbell, Elena Mannes describes specific experiments and has interviewed a number of scientists and musicians, mostly as preparation for her documentary The Music Instinct:  Science and Song, upon which the book is based.  This lends credibility to her writing; her fluid story-telling prose helps too.  She loses some of that credibility (to my mind) in the chapter “Music of the Spheres”, where she compares music to the vibrations of the stars and planets.  I was also bored by the discussions of whether birdsong and whalesong should be considered music – it’s a little too “if a tree falls in a forest…” for my liking.  Still, her explanations of the role and potential roles of music in healing are much more scientifically based than Campbell’s, and though she discusses therapies that are outside of the mainstream, such as psychoacoustic therapy, and brain-wave entrainment, she at least admits that the scientific support for these areas is weak, and the jury is still out on their usefulness.  Overall, this book is worth reading, although I suspect watching the documentary would be a lot more entertaining.

On my bookshelf right now is Thinking Fast and Slow by Daniel Kahneman.  It’s not music-related, and I’ll admit that I’m not very far into the book yet.  But so far, it’s a fascinating account of how we use two very different systems for thinking – one automatic, quick and often highly biased, and a second one that is effortful, slow, calculating, and also very lazy.  Kahneman, a renowned psychologist and Nobel laureate who has written a number of books, has a style that is dense but gripping.  The book is full of quick self-tests to demonstrate the fallibility of our reasoning systems, followed by engaging explanations.

And here are my future reading plans:

I’m itching to read Michael Gazzaniga’s Who’s in Charge? Free will and the Science of the Brain, as soon as it actually gets onto the Vancouver Public Library bookshelves; it’s still listed as “on order”.  It’s based on an idea that I’ve been interested in for some time:  our actions are all controlled by our brains, which are collections of cells, governed by the same deterministic and probabilistic rules as the rest of biology.  So when we choose to do something, isn’t it really just our neurons responding to the action potentials of other neurons, which are triggered somewhere upstream by external stimuli?  Where does free will come into this?  Does it actually exist or is it a figment of our lively imaginations?  My interest in this topic was stimulated by another book, The Mind and the Brain by Jeffrey Schwartz, who brings quantum mechanics into the mix.  I’m not sure what I believe about all this, but I definitely want to read more.

Also on my library hold list is Music Cognition: A Science of Listening by Henjan Honing, a professor of music cognition at the University of Amsterdam.  The book sounds promising, even though it is written for a general audience.  I’ll keep you posted.