And what we've been able to show is that ketamine, by blocking this fast communication, what it does is it actually strengthens particular connections in the brain, what we call synaptic plasticity. It's just a change in your brain.
So neurons firing leads to neurons rewiring. You get less synaptic connections, the connections among neurons, and even less neurons.
gets. For example, your brain is actually more or less uh like a network of um of synaptic um layers of tracks that have firings, electrical firings. So right now if I
And I actually think that's a valid argument. So it helps expand your synaptic connections in your brain.
It can unleash the best in human nature, selfless sacrifice for others. It can augment or inhibit synaptic transmission.
And coincident with that, we looked in the brain, and we would see an increase in new neurons after the treatment. We would see an increase in synaptic plasticity. Even far away in the contralateral part of the brain, this mesenchymal stem cell treatment improved the plasticity and learning of the injured rat.
They have dendrites with more branches. A higher density and complexity of synaptic connections. So what does all of this mean in terms of what should be done differently in terms of design?
The bottom neuron is after learning and after sleep. All of these little triangles or new synaptic connections. And so when you learn something and you go to sleep, that's when the new synaptic connections are forming.
SV2A-- as one progresses from the uninjured brain to the devastated brain. It's important to have non-invasive methods of measuring synaptic activity over time in a patient with brain injuries, especially in order to evaluate new therapies. This marker is but one of many promising approaches to this problem.
But from the auditory domain, visual domain, et cetera, this is coming into our very, very complex brains, and it's changing the weights in our synaptic connections in ways we don't fully understand. And this is really how we operate in the world, generally.
I missed an appointment or like showed up at the wrong time or whatever because of that swapping. So it's really taken a lot of synaptic reorganization to kind of get that, but it's a good point. If you're looking at something from Israel, the first two elements of the date are going to be swapped.
But in the strict sense, in the observer-independent sense in which you and I have intelligence, there is zero intelligence in the computer. But we don't know if you mess around in the synaptic cleft, you're going to get weird effects.
itself fires. And of course, then it sends currents to the neurons downstream. OK? And the synaptic process itself involves chemistry and whatnot, but those details are not important for us. OK? So what's going to happen is that the learning basically happens when a neuron helps to make another neuron fire.
So neurons firing leads to neurons rewiring. Instead of just having the neurons build their synaptic connections with each other pretty progressively throughout childhood, once the switch happens--
So neurons firing leads to neurons rewiring. The brain starts to eliminate not only the synaptic connections that were laid down, some of them, but it actually starts destroying neurons themselves.
Well, Sayem's brain, like all kids brains, is like a new city under construction. And calcium actually plays a role like a city planner directing crews to build synaptic roads and bridges that allow for things like learning and memory and impulse control, all these tools we need.
First, a brain injury must be precisely characterized, both immediately after the event, over time, and in response to treatments. This requires the ability to perform functional imaging with resolution sufficient to detect changes in synaptic activity. Next, there need to be methods to stimulate the formation of new connections.
It can unleash the best in human nature, selfless sacrifice for others. There's got to be enormous communication going on among these cells that is non-synaptic and non-neuronal.
The first challenge that I mentioned was improved functional imaging. New radio tracers have been developed, which let one see areas of decreased or increased synaptic activity. On the left is an image from an uninjured person.
All the way down to the lowest levels, you have things like changes to the expression of genes with the epigenome. But at the top level, you have changes in biochemical cascades and then changes in the synaptic connections strength and so on. But this is the issue, is it's a completely livewired system.
It releases transmitter here and creates a bioelectrical signal that travels towards the soma of the post-synaptic nerve.
so much more effectively. Now, another very important aspect of sleep relates to neural synaptic growth. In this wonderful paper by Guang Yang -- she's out of Langone-- is if you look at the top picture,
All of these little triangles or new synaptic connections. And so when you learn something and you go to sleep, that's when the new synaptic connections are forming. And this is what's going on when you're learning.
amazing is that when I'm talking to you right now, I don't need to worry about manipulating all of the synaptic proteins in your brain to make you understand what I'm saying
Even a failure to remember something, which entails a struggle to recall, actually activates synaptic connections
It can unleash the best in human nature, selfless sacrifice for others. Throughout my career, I've studied how neurons are wired together in development, how they change the strength of their synaptic connections through experience, and how we store memories.
There were more-- you can see you the slide of the neuron, more dendrite, so more synaptic connections if there are more dendritic branches, more glial
But there are a lot of other measures that-- like looking at blood flow, looking at the use of glucose, looking at synaptic growth.
And I'm not talking, hey, I've got to be an Olympic weight-lifter, or be a marathon runner. And by spacing things out, you realize, now, that you're getting those new synaptic connections growing every time you learn a little and then you sleep on it.
So neurons firing leads to neurons rewiring. So the first thing that was found which shocked everyone was that the brain, instead of to continue to develop synaptic connections, actually
So neurons firing leads to neurons rewiring. So the second dozen years of life, of course you continue to learn with laying down new synaptic connections.
is whether the mind is strictly a product of the physical mechanics of the brain; the neurons and synaptic connections. I actually think this, and not evolution, is now the