Essentials: How to Control Your Sense of Pain & Pleasure

**Andrew Huberman** (0:00)
Welcome to Huberman Lab Essentials, where we revisit past episodes for the most potent and actionable science-based tools for mental health, physical health and performance.
I'm Andrew Huberman, and I'm a professor of neurobiology and ophthalmology at Stanford School of Medicine. Today, we continue our discussion of the senses, and the senses we are going to discuss are pain and pleasure. Pain and pleasure reflect two opposite ends of a continuum, a continuum that involves detection of things in our skin, and the perception, the understanding of what those events are. Our skin is our largest sensory organ and our largest organ indeed. It is much larger than any of the other organs in our body. And it's an odd organ if you think about it. It has so many functions. It acts as a barrier between our organs and the outside world. It harbors neurons, nerve cells, that allow us to detect things like light touch or temperature or pressure of various kinds. And it's an organ that we hang ornaments on. People put earrings in their ears. People decorate their skin with tattoos and inks and other things. And it's an organ that allows us to experience either great pain or great pleasure. So it's a multifaceted organ and it's one that our brain needs to make sense of in a multifaceted way. I think we all intuitively understand what pleasure and pain are. Pleasure generally is a sensation in the body and in the mind that leads us to pursue more of whatever is bringing about that sensation. And pain is also a sensation in the body and in the mind that in general leads us to want to withdraw or move away from some activity or interaction. Scientists would call this appetitive behaviors, meaning behaviors that lead us to create an appetite for more of those behaviors and aversive behaviors, behaviors that make us want to move away from something. The organ that we call the skin, as I mentioned earlier, is the largest organ in our body. And throughout that organ, we have neurons, little nerve cells. Now, to be really technical about it, and the way I'd like you to understand it, is that the so-called cell body, meaning the location of a cell in which the DNA and other goodies, the kind of central factory of the cell, that actually sits right outside your spinal cord. So all up and down your spinal cord on either side are these little blobs of neurons, little collections of neurons. They're called DRGs, dorsal root ganglia. A ganglion is just a collection or a clump of cells. And those DRGs are really interesting because they send one branch that we call an axon, a little wire out to our skin. And they have another wire from that same cell body that goes in the opposite direction, which is up to our brain and creates connections within our brain in the so-called brainstem. Okay, these wires are positioned within the skin to respond to mechanical forces. So maybe light touch. Some will only send electrical activity up toward the brain in response to light touch. Others respond to coarse pressure, to hard pressure, but they won't respond to a light feather. Others respond to temperature. So they will respond to the presence of heat or the presence of cold. And still others respond to other types of stimuli, like certain chemicals on our skin. So these neurons are amazing. They're collecting information of particular kinds from the skin throughout the entire body and sending that information up toward the brain. And what's really incredible, I just want you to ponder this for a second. What's really incredible is that the language that those neurons use is exactly the same. The neuron that responds to light touch sends electrical signals up toward the brain. The neurons that respond to cold or to heat or to habanero pepper, they only respond to the particular thing that evokes the electrical response. I should say that they only respond to the particular stimulus, the pepper, the cold, the heat, et cetera, that will evoke an electrical signal. But the electrical signals are a common language that all neurons use. And yet, if something cold is presented to your skin like an ice cube, you know that that sensation, that thing is cold. You don't misperceive it as heat or as a habanero pepper. Okay? So that's amazing. What that means is that there must be another element in the equation of what creates pleasure or pain. And that element is your brain. Your brain takes these electrical signals and interprets them partially based on experience, but also there are some innate, meaning some hardwired aspects of pain and pleasure sensing that require no experience whatsoever. A child doesn't have to touch a flame but once, and the very first time they will withdraw their hand from the flame. The pain and pleasure system don't need prior experience. What they need is a brain that can interpret these electrical signals and somehow create what we call pleasure and pain out of them. So what parts of the brain? Well, mainly it's the so-called somatosensory cortex. The portion of our neocortex, which is on the outside of our brain, the kind of bumpy part. And in your somatosensory cortex, you have a map of your entire body surface. That map is called a homunculus. It's your representation of touch, including pleasure and pain. But it's not randomly organized. It's highly organized in a very particular way, which is that the areas of your skin that have the highest density of these sensory receptors are magnified in your brain. What are the areas that are magnified? Well, the lips, the face, the tips of the fingers, the feet and the genitals. And that's because the innervation, the number of wires that go into those regions of your body far exceeds the number of wires for sensation of touch that go to other areas of your body. You can actually experience this in real time right now by doing a simple experiment that we call two-point discrimination. Two-point discrimination is your ability to know whether or not two points of pressure are far apart, near each other, or you actually could perceive incorrectly as one point of pressure. You might want a second person to do this experiment. That person would take two fine points, so it could be two pencils or pens or the backs of pens. If you were to close your eyes and I were to take these two pens and put their points close together about a centimeter apart and present them to the top of your hand, you, even though your eyes were closed, you would be able to perceive that that was two points of pressure presented simultaneously to the top of your hand. However, if I were to do this to the middle of your back, you would not experience them as two points of pressure. You would experience them as one single point of pressure. In other words, your two point discrimination is better, is higher on areas of your body, which have many, many more sensory receptors. Most of us don't really appreciate how important and what a profound influence this change in density of receptors across our body surface has. You've got sensors in the skin and you've got a brain that's going to interpret what's going on with those sensors. And believe it or not, your subjective interpretation of what's happening has a profound influence on your experience of pleasure or pain. There are several things that can impact these experiences, but the main categories are expectation. If someone tells you this is going to hurt, I'm going to give you an injection right here. It might hurt for a second. That's very different. And your experience of that pain will be very different than if it happened suddenly out of the blue. There's also anxiety, how anxious or how high or low your level of arousal, autonomic arousal, that's going to impact your experience of pleasure or pain, how well you slept and where you are in the so-called circadian or 24 hour cycle. Our ability to tolerate pain changes dramatically across the 24 hour cycle. And as you can imagine, it's during the daylight waking hours that we are better able to tolerate. We are more resilient to pain and we are better able to experience pleasure. At night, our threshold for pain is much lower. In other words, the amount of mechanical or chemical or thermal, meaning temperature stimulated, that can evoke a pain response and how we would rate that response is much lower at night. And in particular, in the hours between 2 a.m. and 5 a.m., if you're on a kind of standard circadian schedule. And then the last one is our genes. Pain threshold and how long a pain response lasts is in part dictated by our genes. So we have expectation, anxiety, how well we've slept, where we are in the so-called 24-hour circadian time and our genes. So let's talk about expectation and anxiety because those two factors can powerfully modulate our experience of both pleasure and pain in ways that will allow us to dial up pleasure, if we like, and to dial down pain, if indeed that's what we want to do. I'd like to take a quick break and acknowledge our sponsor, AG1. AG1 is a vitamin mineral probiotic drink that also includes prebiotics and adaptogens. As somebody who's been involved in research science for almost three decades and in health and fitness for equally as long, I'm constantly looking for the best tools to improve my mental health, physical health, and performance. I discovered AG1 back in 2012, long before I ever had a podcast, and I've been taking it every day since. I find it improves all aspects of my health, my energy, my focus, and I simply feel much better when I take it. AG1 uses the highest quality ingredients in the right combinations, and they're constantly improving their formulas without increasing the cost. 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