How Your Nervous System Works & Changes | Huberman Lab Podcast #1 Flashcards
What is the nervous system?
The reason I say your nervous system and not your brain is because your brain is actually just one piece of this larger, more important thing, frankly, that we call the nervous system. The nervous system includes your brain and your spinal cord but also all the connections between your brain and your spinal cord and the organs of your body. It also includes, very importantly, all the connections between your organs
back to your spinal cord and brain. So the way to think about how you function at every level from the moment you’re born until the day you die, everything you think and remember and feel and imagine is that your nervous system is this continuous loop of communication between the brain, spinal cord, and body and body, spinal cord, and brain. But two guys, that names aren’t super important, but in fairness to their important discovery, Ramon y Cajal, a Spaniard, Camillo Golgi, an Italian guy, figured out how to label or stain the nervous system in a way that revealed, oh my goodness,
we’re actually made up of trillions of these little cells, nerve cells that are called neurons. And that’s what a neuron is. It’s just a nerve cell. They also saw that those nerve cells weren’t touching one another. They’re actually separated by little gaps. And those little gaps you may have heard of before, they’re called synapses.
How does the nervous system communicate?
But the language of the nervous system is just electricity. It’s just like a Morse code of some sort or the syllables and words and consonants and vowels of language. It just depends on how they’re assembled, what order. And so that brings us to the issue of how the nervous system works. The way to think about how the nervous system works is that our experiences, our memories, everything is sort of like the keys on a piano being played in a particular order, right? If I play the keys on a piano in a particular order and with a particular intensity, that’s a given song. We can make that analogous to a given experience. It’s not really that the key, you know, A sharp or E flat is the song. It’s just one component of the song. So when you hear that, you know, for instance, there’s a brain area called the hippocampus, which there is, that’s involved in memory. Well, it’s involved in memory, but it’s not that memories are stored there as, you know, sentences. They’re stored there as patterns of electricity in neurons that when repeated, give you the sense that you are experiencing the thing again. In fact, deja vu, the sense that what you’re experiencing is so familiar and like something that you’ve experienced previously is merely that the neurons that were active in one circumstance are now becoming active in the same circumstance again. And so it’s really just like hearing the same song maybe not played on a piano but next time on a classical guitar, there’s something similar about that song even though it’s being played on two different instruments. So I think it’s important that people understand the parts of their nervous system, and that it includes so much more than just the brain and that there are these things, neurons and synapses. But really that it’s the electrical activity of these neurons that dictates our experience.
What is ment with The brain is really a map of experience?
So that indicates that our brain is really a map of our experience. We come into the world and our brain has a kind of bias towards learning particular kinds of things. It’s ready to receive information and learn that information, but the brain is really a map of experience. So let’s talk about what experience really is. What does it mean for your brain to work? Well I think it’s fair to say that the nervous system really does five things, maybe six.
Nervous system task: Sensing
The first one is sensation. So this is important to understand for any and all of you that want to change your nervous system or to apply tools to make your nervous system work better. Sensation is a non-negotiable element of your nervous system. You have neurons in your eye that perceive certain colors of light and certain directions of movement. You have neurons in your skin that perceive particular kinds of touch, like light touch or firm touch or painful touch. You have neurons in your ears that perceive certain sounds. Your entire experience of life is filtered by these, what we call sensory receptors if you want to know what the name is.
Nervous system task: Perceptions
So we have sensation, then we have perception. Perception is our ability to take what we’re sensing and focus on it and make sense of it, to explore it, to remember it. So really perceptions are just whichever sensations we happen to be paying attention to at any moment. And you can do this right now. You can experience perception and the difference between perception and sensation very easily. If, for instance, I tell you to pay attention to the contact of your feet, the bottoms of your feet, with whatever surface they happen to be in contact with, maybe it’s shoes, maybe it’s the floor, if your feet are up maybe it’s air. The moment you place your, what we call the spotlight of attention or the spotlight of perception on your feet. You are now perceiving what was happening there, what was being sensed there. The sensation was happening all along however. So while sensation is not negotiable you can’t change your receptors unless you adopt some new technology, perception is under the control of your attention.
And the way to think about attention is it’s like a spotlight, except it’s not one spotlight. You actually have two attentional spotlights. Anyone that tells you you can’t multitask, tell them they’re wrong. And if they disagree with you tell them to contact me because in old world primates of which humans are, we are able to do what’s called covert attention.
Attention is something that is absolutely under your control, in particular when you’re rested. And we’ll get back to this. But when you are rested, and we’ll define rest very clearly, you are able to direct your attention in very deliberate ways. And that’s because we have something in our nervous system which is sort of like a two way street. And that two way street is a communication between the aspects of our nervous system that are reflexive (Bottom-up) and the aspects of our nervous system that are deliberate (Top-down).
Nervous system task: Emotions + the chemicals of emotion
So we’ve got sensations, perceptions, and then we’ve got things that we call feelings/emotions. And these get a little complicated because almost all of us, I would hope all of us, are familiar with things like happiness and sadness or boredom or frustration. Scientists argue like crazy, neuroscientists and psychologists and philosophers for that matter, argue like crazy about what these are and how they work. Certainly emotions and feelings are the product of the nervous system. They involve the activity of neurons. But as I mentioned earlier, neurons are electrically active but they also release chemicals. And there’s a certain category of chemicals
that has a very profound influence on our emotional states. They’re called neuromodulators. And those neuromodulators have names that probably you’ve heard of before. Things like dopamine and serotonin and acetylcholine, epinephrine. Neuromodulators are really interesting because they bias which neurons are likely to be active and which ones are likely to be inactive. A simple way to think about neuromodulators is they are sort of like playlists that you would have on any kind of device where you’re going to play particular categories of music.
And we have to consider also that feelings and emotions are contextual. In some cultures showing a lot of joy or a lot of sadness is entirely appropriate, in other cultures it’s considered inappropriate. So I don’t think it’s fair to say that there is a sadness circuit or area of the brain or a happiness circuit or area of the brain.
However, it is fair to say that certain chemicals and certain brain circuits tend to be active when we are in motivated states, tend to be active when we are in non-motivated lazy states, tend to be active when we are focused and tend to be active when we are not focused. I want to emphasize also that emotions are something that we generally feel are not under our control. We feel like they kind of geyser up within us and they just kind of happen to us. And that’s because they are somewhat reflexive. We don’t really set out with a deliberate thought to be happy or a deliberate thought to be sad. We tend to experience them in kind of a passive reflexive way.
Neuro modulator: Dopamine
So for instance, dopamine, which is often discussed as the molecule of reward or joy, it is involved in reward. And it does tend to create a sort of upbeat mood when released in appropriate amounts in the brain. But the reason it does that is because it makes certain neurons and neural circuits as we call them more active and others less active. dopamine more than being a molecule of reward is really more a molecule of motivation toward things that are outside us and that we want to pursue
Neuro modulator: Serotonin
Okay. So serotonin, for instance, is a molecule that when released tends to make us feel really good with what we have, our sort of internal landscape and the resources that we have,
Nervous system task: Thoughts and thought control
And that brings us to the next thing, which are thoughts. Thoughts are really interesting because in many ways they’re like perceptions except that they draw on not just what’s happening in the present but also things we remember from the past and things that we anticipate about the future. The other thing about thoughts that’s really interesting is that thoughts can be both reflexive, they can just be occurring all the time sort of like pop-up windows on a poorly filtered web browser, or they can be deliberate.
Nervous system task: Action
And then finally there are actions. Actions or behaviors are perhaps the most important aspect of our nervous system. Because first of all, our behaviors are actually the only thing that are going to create any fossil record of our existence. And so the fossil record of our species and each one of us is really through action. And that, in part, is why so much of our nervous system is devoted to converting sensation, perceptions, feelings, and thoughts into actions.
The reflexive pathway basically includes areas of the brain stem we call central pattern generators. When you walk, provided you already know how to walk, you are basically walking because you have these central pattern generators, groups of neurons that generate right foot, left foot, right foot, left foot kind of movement. However, when you decide to move in a particular deliberate way that requires a little more attention you start to engage areas of your brain for top-down processing where your forebrain works from the top down to control those central pattern generators so that maybe it’s right foot, right foot, left foot, right foot, right foot, left foot if maybe you’re hiking along some rocks or something. And you have to engage in that kind of movement. So movement, just like thoughts, can be either reflexive or deliberate
Well, when you do something deliberately, you pay attention, you are bringing your perception to an analysis of three things,
-duration, how long something is is going to take or should be done,
-path, what you should be doing,
-outcome, if you do something for a given length of time, what’s going to happen.
Now when you’re walking down the street or you’re eating or you’re just talking reflexively, you’re not doing this what I call DPO, duration, path, outcome, type of deliberate function in your brain and nervous system. But the moment you decide to learn something or to resist speaking or to speak up when you would rather be quiet, anytime you’re deliberately kind of forcing yourself over a threshold, you’re engaging these brain circuits and these nervous system circuits that suddenly make it feel as if something is challenging. Something has changed. Well, what’s changed? What’s changed is that when you engage in this duration, path, and outcome type of thinking or behavior or way of being you start to recruit these neuromodulators that are released from particular areas of your brain, and also it turns out from your body. and they start cuing to your nervous system. Something’s different. Something’s different now about what I’m doing. Something’s different about what I’m feeling.
Neuroplasticity: the Grail of Neuroscientist
And so this is really important to understand because if you want to understand neuroplasticity, you want to understand how to shape your behavior, how to shape your thinking, how to change how you’re able to perform in any context, the most important thing to understand is that it requires top-down processing. It requires this feeling of agitation. In fact, I would say the agitation and strain is the entry point to neuroplasticity. Plasticity itself is just a process by which neurons can change their connections and the way they work so that you can go from things being very challenging and deliberate, requiring a lot of effort and strain, to them being reflexive. And what’s so incredible about the human nervous system in particular is that we can direct our own neural changes. We can decide that we want to change our brain. In other words, our brain can change itself and our nervous system can change itself.
And for any of you that are interested in changing your nervous system so that something that you want can go from being very hard or seem almost impossible and out of reach to being very reflexive, this is especially important to pay attention to. Plasticity in the adult human nervous system is gated, meaning it is controlled by neuromodulators. These things that we talked about earlier, dopamine, serotonin, and one in particular called acetylcholine, are what open up plasticity.
When we want something to happen, however, we want to learn a language, we want to learn a new skill, we want to become more motivated, what do we know for certain? We know that that process of getting neuroplasticity so that we have more focus, more motivation, absolutely requires the release of epinephrine. We have to have alertness in order to have focus and we have to have focus in order to direct those plastic changes to particular parts of our nervous system
The pillar of plasticity
We’re going to have a large number of discussions about neuroplasticity in depth, but the most important thing to understand is that it is indeed a two phase process. What governs the transition between alert and focused and these deep rest and deep sleep states is a system in our brain and body, a certain aspect of the nervous system called the autonomic nervous system. And it is immensely important to understand how this autonomic nervous system works. It has names like the sympathetic nervous system and parasympathetic nervous system which frankly are complicated names because they’re a little bit misleading.
-Sympathetic is the one that’s associated with more alertness.
-Parasympathetic is the one that’s associated with more calmness.
So every 24 hours, we have a phase of our day that is optimal for thinking and focusing and learning and neuroplasticity and doing all sorts of things. We have energy as well. And at another phase of our day we’re tired and we have no ability to focus. We have no ability to engage in duration, path, outcome types of analyses. And it’s interesting that both phases are important for shaping our nervous system in the ways that we want. So if we want to engage neuroplasticity and we want to get the most out of our nervous system we each have to master both the transition between wakefulness and sleep and the transition between sleep and wakefulness.
Leveraging Ultradian Cycles & Self Experimentation
So much has been focused on the value of sleep and the importance of sleep, which is great. But I don’t think that most people are paying attention to what’s happening in their waking states and when their brain is optimized for focus, when their brain is optimized for these DPOs, these duration, path, outcome types of engagements for learning and for changing and when are their brain is probably better suited
for more reflexive thinking and behaviors. And it turns out that there’s a vast amount of scientific data which points to the existence of what are called ultradian rhythms. You may have heard of circadian rhythms. Circadian means, circa, about a day. So it’s 24 hour rhythms because the earth spins once every 24 hours. Ultradian rhythms occur throughout the day and they require less time, they’re shorter. The most important ultradian rhythm for sake of this discussion is the 90 minute rhythm that we’re going through all the time in our ability to attend and focus. And in sleep, we are, our sleep is broken up into 90 minute segments. Early in the night we have more phase one and phase two lighter sleep. And then we go into our deeper phase three and phase four sleep. And then we return to phase one, two, three, four. So all night, you’re going through these ultradian rhythms of stage one, two, three, four, one, two, three, four, it’s repeating. Most people perhaps know that. Maybe they don’t. But you wake up in the morning, these ultradian rhythms continue. And it turns out that we are optimized for focus and attention within these 90 minute cycles so that at the beginning of one of these 90 minute cycles maybe you sit down to learn something new or to engage in some new challenging behavior, for the first five or 10 minutes of one of those cycles it’s well-known that the brain and the neural circuits and the neuromodulators are not going to be optimally tuned to whatever it is you’re trying to do. But as you drop deeper into that 90 minute cycle your ability to focus and to engage in this DPO process and to direct neuroplasticity and to learn is actually much greater. And then you eventually pop out of that at the end of the 90 minute cycle. So these cycles are occurring in sleep and these cycles are occurring in wakefulness.
