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

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Welcome to Huberman Lab Essentials, [music] where we revisit past episodes for the most potent and actionable science-based [music] 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.

Great to be here, too. Thank you so much. >> 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? 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. What are some of the other features of states that represent below the tip of the iceberg? >> Right.

There have been people who have thought of emotions as having just really two dimensions, a 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 evoked 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 um that uh make them, if they have been uh 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 and soothe it. If you had a bad day at work, you might react very differently to it. >> 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?

First of all, um 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. The work that Dayu 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’s 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 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 and 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 Dayu now on her own at NYU, and with her postdoc Annegret Falkner, there’s evidence that the type of fighting that we were that we elicit when we stimulate VMH is offensive aggression that is actually rewarding to male mice.

They like it. >> They like it. Male mice will learn to poke their nose or press a bar to get the opportunity to beat up a subordinate male mouse. It has a positive valence. So, it’s become clear that, if you want to call it the state of aggressiveness, is multifaceted.

It depends on the type of aggression, and it involves different sorts of circuits. Why do you think there would be such a close positioning of neurons that can elicit such divergent states and behaviors? I mean, you’re talking about this pear-shaped structure where the neurons that generate fear are cheek to jowl with the neurons that generate offensive aggression. If you think from an evolutionary perspective, it might have been the case that defensive behaviors and fear arose before offensive aggression, because animals, first and foremost, have to defend themselves from predation by other animals. And maybe it’s only when they’re comfortable with having warded off predation and made themselves safe that they can start about start to think about who’s going to be the alpha male in in my group here.

And so, it could be that, if you think that brain regions and cell populations evolve by duplication and modification of preexisting cell populations, that might be the way that those regions wound up next to each other. But, I think there must be a functional part, as well. So, one thing we know about offensive aggression is that strong fear shuts it down. Whereas, defensive aggression, at least in rats, is actually enhanced by fear. It’s one of the big differences between defensive aggression and offensive aggression.

And maybe these two regions are close to each other to facilitate inhibition of aggression by the fear neurons. We know for a fact that if we deliberately stimulate those fear neurons at the top of the pear, when two animals are involved in a fight, it just stops the fight dead in its tracks, and they go off into the corner and freeze. So, at least hierarchically, it seems like fear is the dominant behavior over offensive aggression. I think that’s the way I tend to think about why these neurons are are all mixed up together. And it’s not just fight and flight.

There are also metabolic neurons that are mixed together in VMH, as well. >> One of the concepts that you’ve raised in your lectures before is this idea of a sort of hydraulic pressure. Maybe it was Conrad I can’t speak now. Excuse me. Konrad Lorenz, Martin, who talked about a kind of hydraulic pressure towards behavi