Essentials: The Biology of Aggression, Mating & Arousal | Dr. David Anderson

**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. And now for my discussion with Dr. David Anderson. David, great to be here, and great to finally sit down and chat with you.

**David Anderson** (0:24)
Great to be here, too. Thank you so much.

**Andrew Huberman** (0:25)
I want to start with something fairly basic, and that's the difference between emotions and states. How should we think about them, and why might states be at least as useful a thing to think about, if not more useful?

**David Anderson** (0:40)
The short answer to your question is that I see emotions as a type of internal state, in the sense that arousal is also a type of internal state, motivation is a type of internal state, sleep is a type of internal state. They change the input to output transformation of the brain. When you're asleep, you don't hear something that you would hear if you were awake. So from that broad perspective, I see emotion as a class of state that controls behavior. The reason I think it's useful to think about it as a state is it puts the focus on it as a neurobiological process rather than as a psychological process.
Many people equate emotion with feeling, which is a subjective sense that we can only study in humans because to find out what someone's feeling, you have to ask them. And people are the only animals that can talk that we can understand. That's how I think about emotion. It's the, if you think of an iceberg, it's the part of the iceberg that's below the surface of the water. The feeling part is the tip.

**Andrew Huberman** (1:52)
What are some of the other features of states that represent below the tip of the iceberg?

**David Anderson** (1:56)
Right. There have been people who have thought of emotions as having just really two dimensions, an arousal dimension and a valence dimension. Ralph Adolphs and I have tried to expand that a little bit to think about components of emotion, particularly those that distinguish emotion states from motivational states because they are very closely related. One of those important properties is persistence. This is something that distinguishes state-driven behaviors from simple reflexes. Reflexes tend to terminate when the stimulus turns off, like the doctor hitting your knee with a hammer. It initiates with the stimulus onset and it terminates with the stimulus offset. Emotions tend to outlast often the stimulus that evoke them. If you're walking along a trail here in Southern California, you hear a rattlesnake rattling, you're going to jump in the air, your heart is going to continue to beat and your palms sweat for a while after it's slithered off in the bush, and you're going to be hypervigilant. If you see something that even remotely looks snake-like, a stick, you're going to stop. Not all states have persistence. So for example, you think about hunger.
Once you've eaten, the state is gone. You're not hungry anymore. But if you're really angry and you get into a fight with somebody, even after the fight is over, you may remain riled up for a long time and it takes you a while to calm down. And then generalization is an important component of emotion states that make them, if they have been triggered in one situation, they can apply to another situation. My favorite example of that is you come home from work and your kid is screaming. If you had a good day at work, you might pick it up and soothe it. And if you had a bad day at work, you might react very differently to it.

**Andrew Huberman** (4:03)
I'd like to talk a bit about aggression, the beautiful work of Dayu Lin and others in your lab. What are your thoughts on aggression, how it's generated, the neural circuit mechanisms, and some of the variation in what we call aggression?

**David Anderson** (4:14)
First of all, the word aggression in my mind refers more to a description of behavior than it does to an internal state. Aggression could reflect an internal state that we would call anger in humans, or could reflect fear, or it could reflect hunger if it's predatory aggression. In the work that Dayou did when she was in my lab, she found a way to evoke aggression in mice using optogenetics to activate specific neurons in a region of the hypothalamus, the ventromedial hypothalamus, VMH, following first the famous Nobel Prize-winning work of Walter Hess.
In Hess' original experiments, he describes two types of aggression that he evokes from cats depending on where in the hypothalamus he puts his electrode, one of which he calls defensive rage. That's the ears laid back, teeth bared and hissing. And the other one is predatory aggression, where the cat has its ears forward and it's like batting with its paw at a mouse-like object, like it wants to catch it and eat it. If you think of ventromedial hypothalamus like a pear sitting on the ground, the fat part of the pear near the ground is where the aggression neurons are, but the upper part of the pear has fear neurons. Fast forward from that, from a lot of work from Dayou now on her own at NYU and with her postdoc, Annegret Faulkner, there's evidence that the type of fighting that we elicit when we stimulate VMH is offensive aggression that is actually rewarding to male mice.