Our brains have an amazing ability to reorganize themselves. We call this ability neuroplasticity, and this is when our neurons reorganize themselves by modifying and forming new connections. Now this is related to synaptic plasticity, which is the ability of neurons to strengthen or weaken their connections based on various activity patterns. And you can see a very simplified version of that here, where we have one neuron that receives stimulation that's going to have some change occur in its synapse, and another neuron that does not receive stimulation and does not change its synapse. So synaptic plasticity is sort of a mechanism that contributes to neuroplasticity. Now one amazing example of neuroplasticity can be seen here, with something known as phantom limb syndrome. With phantom limb syndrome, basically, people who have lost a limb will still experience the presence of the limb there, and that's because even though they've lost the limb very suddenly, their neural networks haven't adapted yet to that change. So one amazing way that people deal with phantom limb syndrome is by using something called a mirror box. It's very common for people with phantom limb syndrome to feel as though the limb they've lost is tensed up and uncomfortable. So, one way they deal with this is by using a mirror box, and they'll have the person, you know, essentially use the hand or, you know, the limb that they still have in the mirror box, and it will appear to them as if it's the limb that they're missing, the phantom limb. And so they can take that limb in the mirror box and they can tense it up, and then ease the tension, and relax it, and it will appear like it's the phantom limb doing that, and that will actually help change their neural networks to get rid of that discomfort. So pretty amazing stuff, neuroplasticity. Also, people with traumatic brain injuries are capable of recovering lost functions due to brain damage by reorganizing other parts of their brain to pick up the slack and carry out those functions that they aren't even supposed to do technically. It's pretty incredible. And, this capacity is much greater when we're younger, and we sort of lose it as we get older, which is why children are so much better able to recover from brain injuries, for example, and also better able to learn things. Now neurogenesis is the growth of new nervous tissue, and this occurs mostly when we're developing embryos. As adults, we really can't produce new nervous tissue; however, there are some small exceptions. Now all of this neuroplasticity, synaptic plasticity is highly related to learning and memory. Now learning is going to be technically acquiring, modifying, or reinforcing some type of knowledge, behavior, or skill. So, you know, you can, for example, learn a new skill, and then you're going to be adapting your brain to that new skill, or you can have a neural network that's already in place for some particular behavior, for example, and reinforce that, make it stronger, strengthen that behavior, so to speak. Memory, on the other hand, is going to be the encoding, storage, and retrieval of information. There are actually different types of memory. We actually have what's known as sensory memory, and this is a very transient type of memory. It's basically, the ability to hold sensory information for just like a second after you perceive it. So for example, if you look at something and then very quickly close your eyes, for a second you hold that image in your mind as if you're still looking at it. That’s sensory memory of what you were just experiencing, the perception that you just had. Now there's also short-term memory, which is the ability to recall a small number of items without actually having to, sort of, rehearse it. Technically, rehearsal is a jargony term, and is, you know, when, for example, if you're trying to memorize something, you repeat it over and over to yourself to just kind of strengthen it in your mind. So, short-term memory is our ability to, you know, kind of, without having to really try to remember things hold just a few limited pieces of information in our mind. In fact, it's thought to be about 7 pieces of information, and that's why telephone numbers are 7 digits long. So, there you go. Now long-term memory is going to be information and knowledge that's stored and recalled for a very long time. In fact, it could be potentially your entire life that you can retrieve this information. And the mechanism behind this long-term formation of memory is thought to be something called long-term potentiation. And this is the long-term strengthening of a synapse based on activity patterns. And it’s extrapolated to be involved in the cellular mechanisms behind learning and memory. Essentially, we're not trying to sit here and tell you that all memory comes from long-term potentiation, but there's definitely some involvement of this process in long-term memory. So what happens with long-term potentiation? Well, essentially,Synapse due to some type of activity pattern, this connection is going to be strengthened. And one of the ways it'll be strengthened is by adding new receptors to the postsynaptic, postsynaptic side of the synapse. And you can see that, here we only had 2 receptors, whereas over on this side here we now have 4 receptors. So that's going to strengthen that synapse. Right? Another thing that can happen is by releasing more neurotransmitter, we will strengthen that connection. See here, we're only releasing a little bit of neurotransmitter. Here, we're releasing a lot more neurotransmitter. So these two effects are gonna add together and result in a much stronger connection at this synapse by a combination of added receptors and added neurotransmitter. So those two facets are going to combine together and produce a much stronger overall response. With that, let's go ahead and turn the page.