Essentials: The Biology of Aggression, Mating & Arousal | Dr. David Anderson
4/9/202638 mincomplete
0:00Welcome to Huberman Lab Essentials, where we revisit past episodes for the most potent and
0:05actionable science -based tools for mental health, physical health, and performance.
0:11I'm Andrew Huberman, and I'm a professor of neurobiology and ophthalmology at Stanford School of
0:16Medicine. And now for my discussion with Dr.
0:19David Anderson. David, great to be here and great to finally sit down and chat
0:23with you. Great to be here too.
0:25Thank you so much. I want to start with something fairly basic, and that's the
0:29difference between emotions and states.
0:31How should we think about them, and why might states be at least as useful
0:37a thing to think about, if not more useful?
0:39The short answer to your question is that I see emotions as a type of
0:45internal state, in the sense that arousal is also a type of internal state.
0:50Motivation is a type of internal state.
0:52Sleep is a type of internal state.
0:55They change the input -to -output transformation of the brain.
0:59When you're asleep, you don't hear something that you would hear if you were awake.
1:04So from that broad perspective, I see emotion as a class of state that controls
1:11behavior. The reason I think it's useful to think about it as a state is
1:16it puts the focus on it as a neurobiological process rather than as a psychological
1:23process. Many people equate emotion with feeling, which is a subjective sense that we can
1:30only study in humans because to find out what someone's feeling, you have to ask
1:37them, and people are the only animals that can talk that we can understand.
1:41That's how I think about emotion.
1:43It's the, if you think of an iceberg, it's the part of the iceberg that's
1:48below the surface of the water.
1:50The feeling part is the tip.
1:52What are some of the other features of states that represent below the tip of
1:56the iceberg? Right. There have been people who have thought of emotions as having just
2:01really two dimensions, an arousal dimension and a valence dimension.
2:07Ralph Adolphs and I have tried to expand...
2:09... ... ... and that a little bit to think about components of emotion, particularly
2:14those that distinguish emotion states from motivational states, because they are very closely related.
2:21One of those important properties is persistence.
2:25This is something that distinguishes state -driven behaviors from simple reflexes.
2:31Reflexes tend to terminate when the stimulus turns off, like the doctor hitting your knee
2:38with a hammer. It initiates with the stimulus onset and it terminates with the stimulus
2:43offset. Emotions tend to outlast often the stimulus that evoke them.
2:49If you're walking along a trail here in Southern California, you hear a rattlesnake rattling.
2:55You're going to jump in the air.
2:57Your heart is going to continue to beat and your palms sweat for a while
3:01after it's slithered off in the bush and you're going to be hypervigilant.
3:05If you see something that even remotely looks snake -like, a stick, you're going to
3:10stop. Not all states have persistence.
3:13So for example, you think about hunger.
3:16Once you've eaten, the state is gone.
3:19You're not hungry anymore. But if you're really angry and you get into a fight
3:25with somebody, even after the fight is over, you may remain riled up for a
3:31long time and it takes you a while to calm down.
3:34And then generalization is an important component of emotion states that make them, if they
3:43have been triggered in one situation, they can apply to another situation.
3:50My favorite example of that is you come home from work and your kid is
3:54screaming. If you had a good day at work, you might pick it up and
3:58soothe it. And if you had a bad day at work, you might react very
4:02differently to it. I'd like to talk a bit about aggression, the beautiful work of
4:06Dayu Lin and others in your lab.
4:08What are your thoughts on aggression, how it's generated the neural circuit mechanisms and some
4:12of the variation in what we call aggression?
4:14First of all, the word aggression, in my mind, refers more to.
4:20a description of behavior than it does to an internal state.
4:26Aggression could reflect an internal state that we would call anger in humans, or could
4:32reflect fear, or it could reflect hunger if it's predatory aggression.
4:39The work that Dayu did when she was in my lab, she found a way
4:43to evoke aggression in mice using optogenetics to activate specific neurons in a region of
4:54the hypothalamus, the ventromedial hypothalamus, VMH, following first the famous Nobel Prize -winning work of
5:02Walter Hess. In Hess's original experiments, he describes two types of aggression that he evokes
5:09from cats depending on where in the hypothalamus he puts his electrode, one of which
5:16he calls defensive rage. That's the ears laid back, teeth bared, and hissing.
5:23And the other one is predatory aggression, where the cat has its ears forward and
5:29it's like batting with its paw at a mouse -like object like it wants to
5:34catch it and eat it.
5:35If you think of ventromedial hypothalamus like a pear sitting on the ground, the fat
5:40part of the pear near the ground is where the aggression neurons are, but the
5:44upper part of the pear has fear neurons.
5:48Fast forward from that, from a lot of work from Dayu now on her own
5:52at NYU and with her postdoc, Anna Gret Faulkner, there's evidence that the type of
5:58fighting that we elicit when we stimulate VMH is offensive aggression that is actually rewarding
6:08to male mice. They like it.
6:11They like it. Male mice will learn to poke their nose or press a bar
6:16to get the opportunity to beat up a subordinate male mouse.
6:21It has a positive valence.
6:24So it's become clear that if you want to call it the state of aggressiveness
6:30is voiceover. The state of aggression is 205.
6:31The state of aggression is 206.
6:31The state of aggression is Thank you.
6:32multifaceted, it depends on the type of aggression, and it involves different sorts of circuits.
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7:41Why do you think there would be such a close positioning of neurons that can
7:46elicit such divergent states and behaviors?
7:49I mean, you're talking about this pear -shaped structure where the neurons that generate fear
7:54are cheek to jowl with the neurons that generate offensive aggression.
7:58If you think from an evolutionary perspective, it might have been the case that defensive
8:05behaviors and fear arose before offensive aggression because animals first and foremost have to defend
8:15themselves from predation by other animals.
8:18And maybe it's only when they're comfortable with having warded off predation and made themselves
8:25safe that they can start to think about who's going to be the alpha male
8:30in my group here. And so it could be that if you think that brain
8:36regions and cell populations evolved by duplication and modification of...
8:43pre -existing cell populations. That might be the way that those regions wound up next
8:50to each other, but I think there must be a functional part as well.
8:54So one thing we know about offensive aggression is that strong fear shuts it down,
9:01whereas defensive aggression, at least in rats, is actually enhanced by fear.
9:07It's one of the big differences between defensive aggression and offensive aggression, and maybe these
9:14two regions are close to each other to facilitate inhibition of aggression by the fear
9:22neurons. We know for a fact that if we deliberately stimulate those fear neurons at
9:27the top of the pair, when two animals are involved in a fight, it just
9:31stops the fight dead in its tracks, and they go off into the corner and
9:35freeze. So at least hierarchically, it seems like fear is the dominant behavior over offensive
9:42aggression. I think that's the way I tend to think about why these neurons are
9:47all mixed up together. And it's not just fight and flight.
9:51There are also metabolic neurons that are mixed together in VMH as well.
9:56One of the concepts that you've raised in your lectures before is this idea of
10:00a sort of hydraulic pressure, or maybe it was Conrad, I can't speak now, excuse
10:04me, Conrad Lorenz, Martin, who talked about a kind of hydraulic pressure towards behavior.
10:10What's really driving hydraulic pressure toward a given state?
10:14One way that is helpful, at least for me, to break this question apart and
10:18think about it is to distinguish homeostatic behaviors that is need -based behaviors where the
10:27pressure is built up because of a need, like I'm hungry, I need to eat,
10:33I'm thirsty, I need to drink, I'm hot, I need to get to a cold
10:39place. It's basically the thermostat model of your brain.
10:43You have a set point, and then if the temperature gets too hot, you turn
10:46on the AC, and if the temperature gets too cold, you turn on the heater
10:50and you put yourself back to the set point.
10:52You can think of this acute Accumulated hydraulic pressure, either being based on something that
10:58you were deprived of creating an accumulating need or something that you want to do,
11:05building up a drive or a pressure to do that.
11:09And the natural way to think about that, at least for me, is as gradual
11:14increases in neural activity in a particular region of the brain.
11:20So, for example, in the area of the hypothalamus that controls feeding, Scott Sternson and
11:26others have shown that the hungrier you get, the higher the level of activity in
11:32that region in the brain.
11:33And then when you eat, boom, the activity goes right back down again.
11:37And I think in the case of aggression, our data and others show that the
11:42more strongly you drive this region of the brain optogenetically, the more of just a
11:50hair trigger you need to set the animal off to get it to fight.
11:55VMH projects to about 30 different regions in the brain, and it gets input from
12:01about 30 different regions. So, I kind of see it as both an antenna and
12:06a broadcasting center. It's like a satellite dish that takes in information from different sensory
12:13modalities, smell, maybe vision, mechanosensation, and then it sort of synthesizes and integrates that into
12:23a fairly low -dimensional, as the computational people call it, representation of this pressure to
12:31attack. And it broadcasts that all over the brain to trigger all these systems that
12:36have to be brought into play if the animal is going to engage in aggression
12:41because aggression is a very risky thing for an animal to engage in.
12:45It could wind up losing, and it could wind up getting killed.
12:49And so, its brain constantly has to make a cost -benefit analysis of whether to
12:55continue on that path or to back off.
12:58As we're talking about aggression and mating behavior, I think hormones.
13:03One of the common myths that's...
13:05out there, and I think that persists, is that testosterone makes animals and humans aggressive
13:11and estrogen makes animals placid and kind or emotional.
13:15And as we both know, nothing could be further from the truth.
13:18The specific hormones that are involved in generating aggression via VMH are things other than
13:26testosterone. Can you tell us a little bit more about that?
13:28Because there's some interesting surprises in there.
13:31When we finally identified the neurons in VMH, that control aggression with a molecular marker,
13:38we found out that that marker was the estrogen receptor.
13:42Other labs have shown that the estrogen receptor in adult male mice is necessary for
13:48aggression. If you knock out the gene in VMH, they don't fight.
13:53And it's been shown, and a lot of this has worked from your colleague Nirao
13:56Shah at Stanford, who is one of my former PhD students, that if you castrate
14:02a mouse and it loses the ability to fight, not only can you rescue fighting
14:09with a testosterone implant, but you can rescue it with an estrogen implant.
14:14So you can bypass completely the requirement for testosterone to restore aggressiveness to the mice.
14:22And as you say, it's because many of the effects of testosterone, although not all,
14:28many of them are mediated by its conversion to estrogen, by a process called aromatization.
14:35It's carried out by an enzyme called aromatase.
14:39In fact, people may have, most of your listeners may have heard of aromatase because
14:44aromatase inhibitors are widely used in female humans as adjuvant chemotherapy for breast cancer.
14:51What's involved in female aggression that's unique from the pathways that generate male aggression?
14:57So we and other labs have studied this in both mice and also in fruit
15:03flies. One thing in mice that distinguishes aggression in females from males is that male
15:09mice are pretty much ready to fight at the drop of a hat.
15:12Female mice only fight when...
15:16they are nurturing and nursing their pups after they've delivered a litter.
15:22And there's a window there where they become hyper -aggressive.
15:26After their pups are weaned, that aggressiveness goes away.
15:30So this is pretty remarkable that you take a virgin female mouse and expose it
15:36to a male, and her response is to become sexually receptive and to mate with
15:40him. And now you let her have her pups and you put the same male
15:45or another male mouse in the cage with her, and instead of trying to mate
15:49with him, she attacks him.
15:50We recently showed in a paper, this is work from one of my students, Meng
15:55Yu Liu, that within VMH in females, there are two clearly divisible subsets of estrogen
16:03receptor neurons. And she showed that one of those subsets controls fighting and the other
16:11one controls mating. This gets into the whole issue of neurons that are present in
16:16females, but not in males.
16:18So this is already showing you some complexity.
16:21The male mouse VMH has both male -specific aggression neurons and generic aggression neurons.
16:28And then the female VMH, the mating cells, are only found in females.
16:33They are female -specific and not found in the male brain.
16:37And so we're trying to find out what these sex -specific populations of neurons are
16:41doing, but that indicates that that is some of the mechanism by which different sexes
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18:13If one observes the mating behaviors of different animals, we know that there's a tremendous
18:18range of mating behaviors in humans.
18:20There can be no aggressive component.
18:23There could be aggressive component.
18:24Humans have all sorts of kinks and fetishes and behaviors, and most of which probably
18:28has never been documented because most of this happens in private.
18:31With that said, when you look at mating behavior of various animals, you see an
18:35aggressive component sometimes, but not always.
18:38Is it species specific? Is it context specific?
18:41And more generally, do you think that there is crosstalk between these different neuronal populations
18:47and the animal itself might be kind of confused about what's going on?
18:50I can't really speak to the issue of whether this is species specific because I'm
18:55not a naturalist or a zoologist.
18:57I've seen, like you have, in the wild, for example, lions when they mate.
19:02I've seen them in Africa.
19:03There's often a biting component of that as well.
19:06One of the things that surprised us when we identified neurons in VMH, VL that
19:12control aggression in males is that within that population, there is a subset of neurons
19:20that is activated by females during male -female mating encounters.
19:25There's some evidence that those female selective neurons in VMH are part of the mating
19:34behavior. If you shut them down, the animals don't mate.
19:38as effectively as they otherwise would.
19:41What happens when you stimulate them, we don't yet know because we don't have a
19:46way to specifically do that without activating the male aggression neurons.
19:51But I think they must be there for a reason because VMH is not traditionally
19:56the brain region to which male sexual behavior has been assigned.
20:01That's another area called the medial preoptic area.
20:05And there we have shown that there are neurons that definitely stimulate mating behavior.
20:12In fact, if we activate those mating neurons in a male while it's in the
20:16middle of attacking another male, it will stop fighting, start singing to that male, and
20:22start to try to mount that male until we shut those neurons off.
20:27So those are the make -love -not -war neurons, and VMH are the make -war
20:32-not -love neurons. And there are dense interconnections between these two nuclei, which are very
20:39close to each other in the brain.
20:41But it's also possible that there are some cooperative interactions between those structures as well
20:48as antagonistic interactions. And the balance of whether it's the cooperative or antagonistic interactions that
20:57are firing at any given moment in a mating encounter, as you suggest, may determine
21:03whether a moment of coital bliss among two lions may suddenly turn into a snap
21:13or a growl and a bearing of fangs.
21:16We don't know that, but certainly the substrate, the wiring is there for that to
21:21happen. When we made that discovery initially, it raised the question in my mind whether
21:26some people that are serial rapists, for example, and engage in sexual violence might in
21:34some level have their wires crossed in some way that these states that are supposed
21:40to be pretty much separated and mutually antagonistic are not and are actually more rewarding
21:46and reinforcing. I'd love to...
21:49talk about this structure, because it seems to be involved in everything, which is the
21:53PAG, the periaqueductal gray. It's been studied in the context of pain.
21:57It's been studied in the context of the so -called lordosis response, the receptivity or
22:02arching of the back of the female to receive intromission and mating from the male.
22:06In particular, I want to know, is there some mechanism of pain modulation and control
22:11during fighting and or mating?
22:15And the reason I ask is that, while I'm not a combat sports person years
22:20ago, I did a little bit of martial arts and it always was impressive to
22:24me how little it hurt to get punched during a fight and how much it
22:28hurt afterwards, right? So there clearly is some endogenous pain control that then wears off
22:34and then you feel beat up.
22:36What's PAG doing vis -a -vis pain and what's pain doing vis -a -vis these
22:40other behaviors? So I think of PAG like a old fashioned telephone switchboard.
22:47There are calls coming in and then the cables have to be punched into the
22:52right hole to get the information to be routed to the right recipient on the
22:57other end of it. Because pretty much every type of innate behavior you can think
23:02of has had the PAG implicated.
23:05In cross -section, the PAG kind of looks like the water in a toilet when
23:09you're standing over an open toilet bowl.
23:12And if you imagine a clock face projected onto that, it's like the PAG has
23:20sectors from one to 12, maybe even more of them.
23:23And in each of those sectors, you find different neurons from the hypothalamus are projecting.
23:29So it could turn out that there is a topographic arrangement along the dorsal ventral
23:35axis of the PAG and the medial lateral axis of the PAG that determines the
23:41type of behavior that will be emitted when neurons in that region are stimulated.
23:46And I think sort of all of the evidence is pointing in that direction, but
23:50by no means has it been mapped out.
23:53Now, the thing that you mentioned about it not hurting when you got beat up
23:57during martial arts, there is a well -known...
23:59There is a well -known...
24:00phenomenon called fear -induced analgesia, where when an animal is in a high state of
24:10fear, like if it's trying to defend itself, there is a suppression of pain responses.
24:17And I'm not sure completely about the mechanisms and how well that's understood, but for
24:25example, the adrenal gland has a peptide in it that is released from the adrenal
24:32medulla, which controls the fight -or -flight responses, and that peptide has analgesic activities.
24:39Now, whether it's called bovine adrenal medullary peptide of 22 amino acid residues, and I
24:46only know about it because it activates a receptor that we discovered many years ago
24:52that's involved in pain, and we thought it promoted pain, but it turns out that
24:56this actually inhibits pain. It's like an endogenous analgesic.
25:01Whether this is happening, this type of analgesia is happening when an animal is engaged
25:07in offensive aggression or in mating behavior, I don't know, but it certainly is possible.
25:16And I don't know whether these analgesic mechanisms are happening in the PAG.
25:22They could also be happening a little further down in the spinal cord.
25:26The PAG is really continuous with the spinal cord.
25:29If you just follow it down towards the tail of an animal, you will wind
25:34up in the spinal cord.
25:36And so it could be that there are influences acting at many levels on pain
25:41in the PAG and in the spinal cord as well.
25:44And it may well be known.
25:45I just don't know it.
25:47I want to distinguish clearly between things that are not known, that I know are
25:52unknown, which is in a fairly small area where I have expertise from things that
25:57may be known, but I'm ignorant of them because I just don't have a broad
26:01enough knowledge base to know that.
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27:14Tell us about tachykinin. I've talked about this a couple times on different podcast episodes
27:19because of its relationship to social isolation.
27:23My understanding is that tachykinin is present in flies and mice and in humans and
27:28may do similar things in those species.
27:31So, tachykinin refers to a family of related neuropeptides.
27:38So, these are brain chemicals.
27:40They're different from dopamine and serotonin in that they're not small organic molecules.
27:46They're actually short pieces of protein that are directly encoded by genes that are active
27:53in specific neurons and not in others.
27:56And when those neurons are active, those neuropeptides are released together with classical transmitters like
28:03glutamate, whatever. Tachykinins have been famously implicated in pain, particularly tachykinin 1, which is called
28:12substance P, one of the original pain modulating.
28:17This is something that promotes inflammatory pain.
28:21And so, we did a...
28:22screen, unbiased screen of peptides, and found indeed that one of the tachykinins, Drosophila tachykinin,
28:30those neurons, when you activate them, strongly promote aggression, and it depends on the release
28:36of tachykinin. Now, the interesting thing is that in flies, just like in people and
28:42practically any other social animal that shows aggression, social isolation increases aggressiveness.
28:51So, putting a violent prisoner in solitary confinement is absolutely the worst, most counterproductive thing
28:57you could do to them.
28:58And indeed, we found in flies that social isolation increases the level of tachykinin in
29:05the brain, and if we shut that gene down, it prevents the isolation from increasing
29:11aggression. So, since my lab also works on mice, it was natural to see whether
29:17tachykinins might be upregulated in social isolation and whether they play a role in aggression.
29:24And this is work done by a former postdoc, Moriel Zelikovsky, now at University of
29:28Salt Lake City in Utah, and she found remarkably that when mice are socially isolated
29:35for two weeks, there is this massive upregulation of tachykinin 2 in their brain.
29:43In fact, if you tag the peptide with a green fluorescent protein from a jellyfish
29:49genetically, the brain looks green when the mice are socially isolated because there's so much
29:55of this stuff released. And she went on to show that that increase in tachykinin
30:03is responsible for the effect of social isolation to increase aggressiveness and to increase fear
30:10and to increase anxiety. And in fact, there are drugs that block the receptor for
30:16tachykinin, which were tested in humans and abandoned because they had no efficacy in the
30:23tests that they were analyzed for.
30:25If you give those drugs to a socially isolated mouse, it blocks all of the
30:31effects of social isolation. It blocks.
30:33the aggression. It blocks the increased fear and the increased anxiety.
30:38And Moriel described it, the mice just look chill.
30:41It's not a sedative, which is really important.
30:44It's not that the mice are going to sleep.
30:47Most remarkably is once you socially isolate a mouse and it becomes aggressive, you can
30:54never put it back in its cage with its brothers from its litter because it
30:59will kill them all overnight.
31:01But if you give it this drug, which is called osanotin that blocks tachykinin 2,
31:08that mouse can be returned to the cage with its brothers and will not attack
31:14them and seems to be happy about that for the rest of the time.
31:18So this is an incredibly powerful effect of this drug.
31:22And I've been really interested in trying to get pharmaceutical companies to test this drug,
31:29which has a really good safety profile in humans, in testing it in people who
31:35are subjected to social isolation stress or bereavement stress.
31:39But it's just very difficult for economic reasons to find a way to get somebody
31:44to test that. As long as we're talking about humans, I'd love to get your
31:47thoughts about human studies of emotion.
31:49I know you wrote this book with Ralph Adolf.
31:51You have this new book.
31:52There are books that are worth reading.
31:54And then there are books that are important.
31:56And I think this book is truly important for the general population to read and
31:59understand. There's a heat map diagram in that book of subjective reports that people gave
32:04of where they experience an emotion or a feeling, a somatic feeling in their body
32:11or in their head or both when they are angry, sad, calm, lonely, et cetera,
32:17et cetera. And I wouldn't want people to think that those heat maps were generated
32:23by any physiological measurement because they were not.
32:26How should we think about the body in terms of states?
32:30And at some point, I'd love for you to comment on that heat map experiment.
32:34This goes back to something called the somatic marker hypothesis that was proposed by Antonio
32:41Damasio, who is a neurologist at USC, the idea.
32:44that our subjective feeling of a particular emotion is in part associated with a sensation
32:55of something happening in a particular part of our body, the gut, the heart.
33:01If there is a physiology underlying these heat maps, it could reflect increased blood flow
33:06to these different structures. And that in turn reflects communication between the brain and the
33:13body and it's bi -directional communication.
33:16And it's mediated by the peripheral nervous system, the sympathetic and the parasympathetic nervous system,
33:24which control heart rate, for example, blood vessel, blood pressure.
33:29And those neurons receive input from the hypothalamus and other blood brain regions, central brain
33:37regions that control their activity.
33:39And when the brain is put in a particular state, it activates sympathetic and parasympathetic
33:47neurons, which have effects on the heart and on blood pressure.
33:53These in turn feed back onto the brain through the sensory system.
33:58And a large part of this bi -directional communication is also mediated through the vagus
34:05nerve, which many of your listeners and viewers may have heard about because it's become
34:10a topic of intense activity now.
34:13The vagus nerve is a bundle of nerve fibers that comes out basically of your
34:20skull, out of the central nervous system, and then sends fibers in to your heart,
34:28your gut, all sorts of visceral organs.
34:31That information is both afferent and efferent.
34:36The vagal fibers sense things that are happening in the body.
34:41So the reason you feel your stomach tied up in knots if you're tense is
34:47that those vagal fibers are sensing the contraction of the gut muscles.
34:53They're also afferents, which means that So the vagus nerve is To make the vagus
34:55nerve and the vagus nerve are the vagus nerve.
34:55Thank you. information coming out of the brain can influence those peripheral organs as well.
35:01And there's work from a number of labs just in the last six months or
35:07so where people are starting to decode the components of the different fibers in the
35:14vagus nerve. And it's amazing how much specificity is.
35:18There are specific vagal nerves that go to the lung, that control breathing responses that
35:25go to the gut, that go to other organs.
35:28It's almost like a set of color -coded lines, labeled lines for those things.
35:35And now how those vagal afferents play a role in the playing out of emotion
35:42states is a fascinating question that people are just beginning to scrape the surface of.
35:49But I think what's exciting now is that people are going to be developing tools
35:53that will allow us to turn on or turn off specific subsets of fibers within
35:59the vagus nerve and ask how that affects particular emotional behaviors.
36:04So you're absolutely right. This brain -body connection is critical, not just for the gut,
36:09but for the heart, for the lungs, for all kinds of other parts of your
36:14body. And Darwin recognized that as well.
36:17And I think it's a central feature of emotion state.
36:22And I think what underlies are subjective feelings of an emotion.
36:26David, I have to say, as a true fan of the work that your lab
36:30has been doing over so many decades, I know I speak on behalf of a
36:34tremendous number of people. And I say thank you for taking time out of your
36:38important schedule to share with us what you've learned.
36:40I really have appreciated your questions.
36:43They've all been right on the money.
36:45You've hit all of the critical, important issues in this field.
36:49And you've uncovered what is known, the little bit is known, and how much is
36:56not known. And I think it's important to emphasize the unknown things because that's what
37:02the next generation of neuroscientists has to solve.
37:06And so I Hope this will help to attract young people into this field because
37:11it's so important, particularly for our understanding of mental illness and mental health and psychiatry.
37:20We've got to figure out how emotion systems are controlled in a causal way if
37:26we ever want to improve on the psychiatric treatments that we have now.
37:30And that's gonna require the next generation of people coming into the field.
37:35Absolutely, I second that. Well, thank you.
37:37It's been a delight. Thank you.
37:39Great. Really appreciate it.