Full transcript of neuroscientist Max Cynader’s TEDx Talk: Enhancing The Plasticity of The Brain at TEDxStanleyPark Conference.
Right click to download the MP3 audio:
Max Cynader – Director of the Brain Research Centre
Thank you very much for that generous introduction. It’s a pleasure to be here.
Today my subject is “Enhancing Brain Plasticity.” And what I’m going to do in the next few minutes hopefully is to tell you a little bit about what brain plasticity is, how it works, what we’re doing to try to enhance it, and what you can do to enhance the plasticity of your brain. So at end of these 18 minutes, I hope that all of that will transpire.
So, what is brain plasticity? Well, brain plasticity is the process by which your brain changes depending on what has happened to it. And brain plasticity would include, for instance, memory. If you remember this lecture tomorrow — and I hope you will — it’s because of brain plasticity.
But brain plasticity is more than memory. It’s the process by which your brain is involved in learning, say a new skill, learning to ski or play Sudoku; do things like that. It’s the process by which you recover from brain damage of various sorts, for instance, after a neurotrauma or a stroke and it’s also how you adapt to the fact that you now weigh 20 pounds more after Christmas, and all your biomechanics are different, yet you still have to walk gracefully. So all of that is brain plasticity.
Now, most of what you need to learn about brain plasticity in this talk can be summarized in the following slogan, OK? So after this, you can just go to sleep — the slogan is “Neurons that fire together wire together.” Contiguity breeds connectivity. And this is a lesson that has been learned in the last 20 or 30 years of neuroscience research. I’m going to tell you a little bit about just how that actually works.
So let’s focus at the beginning on one part of neuroplasticity, the plasticity that we think of as memory. So what’s a memory, anyway? What is a memory? Well, I submit to you that a memory is nothing more than your ability to reconstruct the whole from a degraded fragment. Nothing more than that. So what do I mean by that?
Let’s talk about a specific memory. How about the memory of, I don’t know, your grandmother? OK. You see all these points of light behind you. Imagine that they’re all points of activity inside your brain. So if you look at this part of the brain here in the back, the visual cortex, imagine that this is what your grandmother looked like, the activity that your grandmother evokes in your visual cortex, during your interaction with her.
Here’s the auditory cortex, and this is the sound of her voice, or the things, the wise things she said to you. You know, this is the parietal cortex, the somatosensory cortex, this is the touch of her skin, the texture of her clothes. Up here in the smell cortex is the smell of her perfume, things like these. So all of these points of light represent activity that occurs in your brain while you’re interacting with your grandmother.
And now remember the slogan: “Neurons that fire together wire together.” So as you interact with your grandmother over the years, the sound of her voice, the texture of her clothes, what she looks like, the smell of her perfume, the taste of her cookies, all those things associate. They come together, they’re active at the same time, and neurons that fire together wire together.
Many of you have probably not seen your grandmother for a very long time. She may be dead. So what happens? You’re walking, I don’t know, along Robson Street, and you walk past the store, and you smell the perfume. Out of that store comes the perfume. And what happens? Your grandmother is right there. All of her is right there: the sound of her voice, what she looks like, the texture of her clothes, all the other attributes of your grandmother can be evoked just by stimulating one part of it. And that’s because neurons that have been firing together for years have now wired together. You can enter the circuit at any point. A piece of music that your grandmother liked is enough to activate that circuit as well. A picture of her is enough to activate it. And that’s what we think is a key part of the memory process, and that’s why neurons firing together are so important.
So in neuroscience now we can actually make neurons — Here we have two neurons, and these neurons are in a mouse brain, but what we’ve done is we’ve taken two neurons, and we’ve stuck into them a gene that we borrowed from jellyfish. It’s the gene that makes jellyfish glow green at night, and we’ve stuck it into these two neurons, and now they too are glowing green, and you can see two neurons connected to each other. The soma is the cell body, the axon is the sending end of the neuron, the dendrite is the receiving end of the neuron.
And what we can do is we can take these two neurons, and force them to associate. We can take the neuron on the left and tickle it with an electrical stimulus, zap! zap! zap!, we make it fire. And if we make it fire hard enough, we can get through the axon, we can activate the next neuron, the neuron on the right. Neurons that fire together wire together. So we go prrp! prrp! prrp! and after a time, what we find is if we make those two neurons associate that the connection between them will get stronger, and we’re understanding the mechanisms by which that works.
Now the way in which the two neurons connect to each other is right over here at a place called the synapse. And over the last decades, neuroscience has really understood the synapse in ways that were just not possible before. So the next slide gives you an illustration of what the synapse looks like. Those little blue dots on the top are the transmitters released by the axon, and then they activate all of these receptors, and all of that machinery in the next neuron, and ultimately that causes the neuron to fire.
But you know there is much more to it. It’s these receptors that are actually very important. You see this receptor? It’s called an AMP receptor. It’s kind of boring. If you put more in, more comes out. In other words, if you give it a weak stimulus, it gives a weak response, if you give it a stronger stimulus, it gives you a stronger response, if you give it a really strong stimulus, it gives you a really strong response called linear.
Look at this kind, the NR receptor, and NMDA receptor it’s also called. It’s very interesting. Very undemocratic receptor. It hates weak inputs: you give it a weak input not only does it not respond, but it actually goes negative. You give it a slightly stronger input; still not very interesting. You give a strong input; it goes crazy. And when it goes crazy, what it does is it activates all this machinery down here, and the effect of all that machinery is to put in more of these ordinary boring receptors.
So what that means is if you can tickle the fancy of this NMDA receptor, you’ll put in more of these ordinary AMPA receptors into the synapse, and then the synapse will become stronger. And that actually seems to be the core mechanism of memory, of strengthening connections between two neurons, of how strong inputs and contiguity can result in a stronger synapse. And that’s actually how we think you remember today’s lecture.
“So OK, Max. That’s all been great biochemistry. I’m all excited. Fine. Good. Well, what have you done for me lately? How’s my memory going to improve from all this?” OK. So I can tell you that scientists are working very hard. All of this understanding is leading to new strategies and therapies. If you actually look here, it turns out that if you block this, this is very important in getting this whole process to happen. We’re working on drugs that will tickle this pathway to give you a better memory. But we’re not there yet.
OK, it turns out that there’s a crucial structure in your brain that seems to be actually very important for your memory. It’s called the hippocampus. So they’re all these points of light on the outside of your cortex. They all funnel down to the hippocampus which again represents the memory trace in a compressed and higher form. We can now record the activity of hundreds of points in the hippocampus, hundreds of cells, as animals, for instance, run through a maze.