back to indexUnderstanding & Controlling Aggression | Huberman Lab Podcast #71
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Welcome to the Huberman Lab Podcast,
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where we discuss science and science-based tools
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for everyday life.
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I'm Andrew Huberman,
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and I'm a professor of neurobiology and ophthalmology
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at Stanford School of Medicine.
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Today, we are discussing aggression.
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I'm going to explain to you
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that there are several different types of aggression.
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For instance, reactive aggression
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versus proactive aggression,
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meaning sometimes people will be aggressive
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because they feel threatened or they are protecting those
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that they love who also feel threatened.
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There's also proactive aggression
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where people go out of their way
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to deliberately try and harm others.
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And there is indirect aggression,
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which is aggression not involving physical violence,
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for instance, shaming people and things of that sort.
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It turns out that there are different biological mechanisms
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underlying each of the different types of aggression.
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And today I will define those for you.
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I'll talk about the neural circuits in the brain and body
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that mediate each of the different kinds of aggression,
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talk about some of the hormones and peptides
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and neurotransmitters involved.
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I promise to make it all accessible to you,
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even if you do not have any biology or science background.
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I will also discuss tools,
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psychological tools and biological tools
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that one can use to better control aggression.
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Now, right here at the outset,
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I want to acknowledge that any discussion about aggression
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has to have an element of context within it.
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To be fair, human beings invest a lot of money,
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a lot of time and a lot of energy,
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and indeed can even derive pleasure from aggression.
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Later, I'll talk about neural circuits in the brain and body
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that reinforce, in other words,
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reward through the release of chemicals
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that make people feel good, acts of aggression.
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However, what I'm mainly referring to
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is the context in which human beings will pay money
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in order to derive what we call vicarious aggression.
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To put it simply, people spend an enormous amount of money
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and time and energy watching other people engage in,
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for instance, aggressive sports.
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And we know that observing your team winning
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over another team causes the release of neurochemicals
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in your brain and body that make you feel good,
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and yes, that can make you feel more aggressive.
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We also know, of course,
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that most governments invest many billions,
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if not trillions of dollars in infrastructure technologies
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and human beings in order to engage in aggression if needed,
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so-called military warfare, et cetera.
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So today's discussion will include a description of aggression
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in the pathological sense.
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We'll actually talk about an explosive aggressive disorder
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that most of you probably haven't heard of,
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but is actually far more common than perhaps you know.
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We'll talk about the role of things
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like attention deficit hyperactivity disorder
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and how that can relate to aggression
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through the relationship between impulsivity
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And we'll talk about verbal aggression,
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physical aggression, proactive aggression
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as mentioned before, and reactive aggression.
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I'm certain that by the end of the episode,
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you will come away with a much more thorough understanding
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of what this thing that we call aggression really is.
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And when you see it in other people,
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I think it will make more sense to you.
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And when you observe it in yourself
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or the impulse to engage in aggression,
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verbal or physical or otherwise,
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I hope that you'll understand it better as well.
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And of course, the tools that I will describe
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should allow you to modulate and control
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aggressive tendencies or predispositions to aggressiveness,
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and just generally to be able to engage with people
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in a more adaptive way overall.
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Before we begin, I'd like to emphasize that this podcast
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is separate from my teaching and research roles at Stanford.
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It is however, part of my desire and effort
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to bring zero cost to consumer information
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about science and science-related tools
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to the general public.
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In keeping with that theme,
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I'd like to thank the sponsors of today's podcast.
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Let's talk about aggression.
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I think that many people out there are put off by aggression
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although others are drawn to aggression,
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both in themselves and when observing it in others.
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The reason to talk about aggression is that,
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as mentioned before,
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the context of aggression really matters.
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So there are instances where aggression is adaptive.
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For instance, a mother protecting her children,
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if she's being attacked
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or if her children are being threatened,
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I think most people would agree
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that so-called maternal aggression of that sort,
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provided the context is right, is a great thing.
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Protecting our young is, after all,
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one of the primary adaptive drives of our species,
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and thank goodness it is.
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Of course, other forms of aggression
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like unprovoked proactive aggression,
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somebody simply being violent to somebody else,
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even when unprovoked.
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Most of us cringe when we see that kind of behavior.
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It can even evoke aggression in people
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when they observe that kind of behavior.
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So again, context really matters,
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but a more general and perhaps an even more important reason
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to think about and understand aggression
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is that by understanding the biology
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and psychology of aggression,
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you will be in a much better position
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to understand how all emotional states come to be,
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both in yourself and in others.
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For instance, many of you have probably heard the statement
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that I believe arises from pop psychology,
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not from formal academic psychology,
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that aggression is just sadness.
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It's a form of sadness that's amplified,
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and it shows up as aggression.
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But when we look at the underlying biology
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and the peer-reviewed literature on this,
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nothing could be further from the truth.
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We have distinct circuits in the brain
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for aggression versus grief and mourning.
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Those are non-overlapping.
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Now, that doesn't mean that you can't be sad and aggressive
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or in a state of mourning and aggressive at the same time.
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But the idea that sadness and aggression
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are one and the same thing is simply not true.
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And by understanding that,
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or perhaps by understanding that irritability and aggression
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are not the same thing,
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you'll be in a much better position to apply
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some of the tools that we will talk about in this episode
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in order to be able to reduce or eliminate,
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or if it's adaptive to you, to modulate aggression.
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And yes, there are cases where modulating your aggression,
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in some cases even amplifying aggression, can be adaptive.
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Now, this of course is not the first discussion
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about the biology of aggression
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or the psychology of aggression.
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And we really can look to the beginning of the last century
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as the time in which the formal study of aggression
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One of the names that's most associated
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with the formal study of aggression
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is none other than Konrad Lorenz.
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Some of you may be familiar with that name.
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Others of you may not be familiar with that name.
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Konrad Lorenz studied so-called imprinting behaviors
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and fixed action pattern behaviors.
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He's most famous, at least in scientific circles,
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for getting geese to believe that he was their parent.
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And if you were to put into Google Konrad with a K Lorenz,
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just as it sounds, Konrad Lorenz geese,
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you're going to see a lot of photos of Konrad
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walking down roads with a lot of geese following him
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or swimming in lakes with a lot of geese following him.
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He had a habit of geese adopting him
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because of the behaviors that he partook in.
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So he would swim out on a lake
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in front of a bunch of little geese,
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and then they would think that he was the parent
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and they would imprint on him.
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He even lived with these animals and they lived with him.
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Sort of a strange character from what I hear.
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But nonetheless, all this work was deserving
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of a Nobel prize because what he discovered
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were fixed action patterns.
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That is patterns of behavior that could be evoked
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by a single stimulus, okay?
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This is really important.
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The idea that you can get a whole category of behaviors,
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like swimming behind a parent
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or looking to somebody for comfort and only them.
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The idea that you could get a huge category
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of different behaviors in a bunch of different contexts
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triggered by just the presence of that person is remarkable
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because what it suggested and what turns out to be true
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is that there are neural circuits,
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not just individual brain areas,
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but collections of brain areas that work together
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to engage a pattern of behaviors.
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And that's the first fundamental principle
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that we need to define today.
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That when we talk about aggression,
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we're talking about activation of neural circuits,
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not individual brain areas,
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but neural circuits that get played out in sequence,
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like keys on a piano.
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But that playing out in sequence means that aggression
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is a verb, it has a beginning, a middle, and an end,
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and it's a process, it's not an event.
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And as you'll see, that turns out to be very important
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in terms of thinking about how one can halt aggression,
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prevent it from happening before it's initiated,
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or maybe even prolonging aggression if that's what's needed.
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Now, Konrad Lorenz had no real knowledge of neural circuits.
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I mean, obviously he knew there was this thing
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that we call a brain and a nervous system,
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and he knew that there were chemicals in the brain
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and hormones and things of that sort
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that were likely to play a role,
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but he really didn't take any measures
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to define what the neural circuits were.
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Frankly, he didn't need to.
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He had his Nobel Prize and he did all this beautiful work.
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He's known for an abundance of work,
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but he did think about what sorts of underlying processes
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could drive something like aggression.
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And he talked about one particular feature
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that's especially important,
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and that's this notion of a pressure.
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The idea that, yes, certain hormones will bias somebody
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or an animal to be aggressive.
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Certain neurotransmitter states,
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and you'll learn what those are today,
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will bias somebody to be more or less aggressive,
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maybe even submissive and passive,
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maybe outright proactively aggressive
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towards anyone or anything in front of them.
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And yes, of course, there will be historical features
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based on their childhood, et cetera, et cetera.
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He understood that there will be a constellation of things
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that would drive people to be aggressive.
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And he described a so-called pressure,
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almost like a hydraulic pressure.
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Just think about fluid pressure in a small container
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being pushed, pushed, pushed until the can
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or the container is ready to explode,
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and how multiple features, multiple variables
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could impinge on that and create that pressure.
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It turns out that's exactly the way the system works.
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There is no single brain area
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that flips the switch for aggression,
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although we'll soon talk about a brain structure
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that generally houses the propensity
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and the output of aggression.
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This notion of a hydraulic pressure
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that can drive us toward aggressive behavior,
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or conversely can be very low pressure
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and keep us in a state of non-reactivity,
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maybe even passivity or submissiveness,
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is a very important feature because it really captures
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the essence of how neural circuits work
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when we're talking about primitive behaviors generally.
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And you can start to notice this in yourself and in others.
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You can start to notice
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when you are veering toward aggression
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or when someone is veering toward aggression,
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verbal or physical.
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Now, that veering is the buildup of this hydraulic pressure
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that Lorenz was referring to,
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and it really does have an underlying biological basis.
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Now, it was some years later
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that the first experiments came along,
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which really started to identify the brain areas
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and the biological so-called pressures
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that can induce aggressive behavior.
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And the person that really gets credit for this
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is a guy by the name of Walter Hess,
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who at that time was working on cats.
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And I know that when you say working on cats,
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a lot of people will cringe,
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a lot of people have cats as pets,
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and certainly cats can be delightful.
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Some people like them more, some people like them less.
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Most people cringe at the idea of doing experiments on cats.
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I should say that these days,
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very few laboratories work on cats.
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Most laboratories that work on animal models
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will work on flies, Drosophila fruit flies
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for their capacity to do genetics,
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on laboratory mice, sometimes rats, but usually mice.
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And occasionally you'll find a lab
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that still works on cats.
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Back in the time of Hess,
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very few laboratories worked on mice.
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Most laboratories worked on cats or rats.
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And the reason for that is nowadays,
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most laboratories use mice if they use animal models
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because of the genetic tools that exist in mice
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to knock out this gene or knock in this gene, et cetera,
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which can't be done in humans or non-human primates,
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at least not very easily at this point in history.
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So when I say he was working on cats,
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I realized that probably evoked some negative emotions
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in some of you, maybe even aggression in some of you.
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What we can do, however, is look at the data
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and make use of the data in terms of our understanding.
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What Hess did was he had cats that were awake
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and he was able to lower stimulating electrode
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Now, keep in mind that the brain
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does not have any pain sensors.
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So after a small hole is made in the skull,
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electrodes are lowered into the brain.
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This is what's done commonly in human neurosurgery.
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And he was able to stimulate different brain areas.
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And he was sort of poking around.
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And when I say sort of,
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he was doing this with some logical intent and purpose.
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He wasn't just poking around in there for fun.
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He was trying to identify brain regions
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that could generate entire categories of behavior,
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a la Lorenz, right?
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These fixed action pattern behaviors.
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Eventually, his electrode landed in a site
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and he provided electrical stimulation to the cat
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that caused this otherwise passive purring, relaxing cat
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to suddenly go into an absolute rage.
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So arched back, hissing, hair up,
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so-called pyloerection where the hairs go up.
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Animals try and make themselves as big as possible,
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often when they're aggressive.
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Drooling, maybe even spitting, believe it or not,
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cats and other animals can do this.
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And the cat tried to attack him and anyone else
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and anything else, even inanimate objects
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when he stimulated this particular brain area.
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So Hess obviously took notice
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of this incredible transformation in behavior.
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And the fact that when he turned off the stimulation
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of this particular brain area,
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the cat very quickly within seconds
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went back to being passive calm kitty.
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Now, of course, he repeated this experiment in other animals
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because he had to confirm that it wasn't just happenstance,
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that there wasn't something unique about this one cat
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that perhaps he had stimulated an area
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that had been built up during the kittenhood
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of this cat and had been reactivated.
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Maybe this kitten had been traumatized early in life
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or scared and reactivation of a particular circuit
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unique to that cat created this aggressive behavior.
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That wasn't the case.
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Every cat that he looked at
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and stimulated this particular brain area,
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the cat would immediately go into an aggressive,
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almost rage-type behavior.
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Now, of course, we can't anthropomorphize.
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We don't know what the cat was feeling.
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For all we know, the cat could be happy,
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although that seems pretty unlikely.
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And later experiments done in mice, but also in humans,
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confirm that indeed stimulation of this brain area
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evoked not just behavioral aggression,
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but also subjective feelings of aggression and anger.
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So what was this incredible brain area?
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Or rather, I should say, what is the brain area
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that harbored this incredible capacity
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to generate aggressive behavior in Hess's experiments?
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Well, for those of you that are regular listeners
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to this podcast, you'll probably be relieved to know
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that today we're going to talk about
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some new neural circuits.
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Oftentimes we'll center back on the amygdala
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or the prefrontal cortex, and those names will come up.
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And for those of you that haven't heard them before,
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don't worry, I'll make it clear
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as to what those brain areas are and what they do.
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But today we're going to talk a lot about
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the so-called VMH or ventromedial hypothalamus.
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The ventromedial hypothalamus is a nucleus,
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meaning a small collection of neurons.
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And that small collection of neurons
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that we call the ventromedial hypothalamus is truly small.
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It's only about 1,500 neurons on one side of your brain
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and a matching 1,500 neurons
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on the other side of your brain.
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And that combined 3,000 neurons or so,
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it's not exactly 3,000, but 3,000 neurons or so
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is sufficient to generate aggressive behavior
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of the sort that Hess observed in the cat.
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And believe it or not,
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when you see somebody who's in an act of rage
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or in an act of verbal aggression
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or in an act of defensive aggression,
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protecting their family or loved ones or country, et cetera,
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almost certainly those neurons are engaged in that behavior.
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Those neurons are perhaps even generating that behavior.
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And next I'll describe some experiments
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that were done just recently within the last 10 years or so,
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but leading right up until this year and even last month
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that keep confirming again and again and again
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that it is the activity of neurons
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in the ventromedial hypothalamus
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that are both necessary and sufficient
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to generate the full catalog of aggressive behaviors.
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Now, before I go further to describe
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the beautiful recent studies on the VMH,
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the ventromedial hypothalamus
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and the important role of testosterone
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and more importantly estrogen
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in the activation of aggressive behavior.
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That's soon to be clear to you why that's the case.
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I want to emphasize that the ventromedial hypothalamus
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is something that we should all care about.
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Well, it turns out that many categories
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of psychiatric disorders, developmental disorders
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and psychological challenges,
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things like schizophrenia, PTSD,
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post-traumatic stress disorder, depression,
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borderline personality disorder,
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and even certain forms of autism
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can include elements of aggression and even violence.
link |
Now, it's certainly not the case
link |
that aggression and violence are present
link |
in all people who suffer from schizophrenia or PTSD
link |
or depression or autism or borderline personality disorder.
link |
I'm absolutely not saying that.
link |
However, it can be a feature of those
link |
and it's a well-described feature
link |
in terms of trying to understand the constellation
link |
of challenges that people suffer from when they have those.
link |
So thinking about the VMH goes way beyond
link |
just understanding basic aggression
link |
in the context of adaptive aggression.
link |
So, you know, when earlier I use the example
link |
of maternal aggression,
link |
that's one adaptive form of aggression.
link |
It also can be pathologic aggression,
link |
meaning it can harm ourselves or others.
link |
So keep this in mind as we go forward
link |
because later we're going to talk about specific tools
link |
designed to modulate or prevent aggression
link |
people with attention deficit hyperactivity disorder
link |
and especially kids with ADHD.
link |
In the meantime, let's return to the VMH,
link |
this relatively small collection of neurons.
link |
And the reason I say relatively small is,
link |
well, your brain has many hundreds of billions of neurons,
link |
maybe even trillions of neurons.
link |
The exact number of neurons isn't really clear,
link |
And it certainly is a lot relative to the number of neurons,
link |
this 3000 or so neurons living in your hypothalamus
link |
that can evoke this aggressive response.
link |
Experiments done by David Anderson's lab at Caltech
link |
were really the first to parse the fine circuitry
link |
and to really show that the ventromedial hypothalamus
link |
is both necessary and sufficient for aggressive behavior.
link |
These are important experiments
link |
and they're worth knowing about.
link |
What they did was they identified,
link |
first of all, where the ventromedial hypothalamus
link |
That was pretty straightforward to do,
link |
sort of known before they started these experiments.
link |
And then they analyzed which genes,
link |
meaning which DNA, which of course becomes RNA
link |
and RNA becomes protein,
link |
which DNA and therefore which proteins are expressed
link |
in particular cells of the ventromedial hypothalamus.
link |
And it turns out that there's a particular category
link |
of neurons in the ventromedial hypothalamus
link |
that make an estrogen receptor.
link |
And it is those neurons in particular
link |
that are responsible for generating aggressive behavior.
link |
How did they know this?
link |
Well, they used a tool that's actually been described
link |
by a previous guest of this podcast.
link |
We had an episode with the psychiatrist and bio engineer
link |
and my colleague at Stanford School of Medicine,
link |
He and others have developed tools
link |
that allow people to control the activity of neurons
link |
essentially by remote control,
link |
by shining light on those neurons.
link |
So in the context of an experiment on a mouse,
link |
which is what David's lab did,
link |
and these were the beautiful experiments of Dai Yu Lin,
link |
who's now in her own laboratory at New York University,
link |
put a little fiber optic cable down into the brain
link |
of the hypo, into the hypothalamus that is of the mouse.
link |
The mouse is able to move around in its cage, freely moving.
link |
Even though it has a little tether, this little wire,
link |
it's a very thin wire.
link |
And that little thin wire is actually a little,
link |
what we call optrode.
link |
And the experimentalist, in this case, Dai Yu,
link |
was able to stimulate the turning on
link |
of a little bit of blue light.
link |
And that blue light activated
link |
only those estrogen receptor neurons
link |
in only the ventromedial hypothalamus.
link |
And the way she was able to do that
link |
is she had introduced a gene
link |
that had been developed by our friend, Carl Deisseroth,
link |
that allows light to trigger electrical activity
link |
So if any of that is confusing
link |
or if all of that is confusing, here's the experiment.
link |
There's a mouse in a cage,
link |
has a little wire coming out of its head.
link |
It doesn't notice, believe it or not.
link |
We know this because it's still eating and mating
link |
and doing all the things that mice like to do
link |
on a daily basis and sleeping, et cetera.
link |
And the mere pressing of a button
link |
will activate a little bit of light released
link |
at the end of that wire.
link |
That light activates particular neurons.
link |
In this case, it's the estrogen receptor-containing neurons
link |
in only the ventromedial hypothalamus.
link |
When that mouse is in a cage with another mouse,
link |
a couple of things happen,
link |
depending on what the other mouse is,
link |
or we could say who the other mouse is.
link |
If it's a male mouse
link |
and you put it in there with a female mouse,
link |
the male mouse will attempt to mate with a female mouse.
link |
Provided that the male mouse has gone through puberty,
link |
he will try to mount and mate with a female mouse.
link |
Now, female mice are either in a receptive phase
link |
or a non-receptive phase of their so-called estrous cycle.
link |
They don't have a menstrual 28-day cycle.
link |
They have an estrous cycle.
link |
And on particular days of that estrous cycle,
link |
they are not happy to mate.
link |
They will basically keep their hindquarters
link |
away from the male mouse at all costs.
link |
They'll even attack the male mouse.
link |
On certain days of the estrous cycle, however,
link |
the female mouse will undergo what's called lordosis,
link |
which is an arching of her back,
link |
and she'll allow the male to mount and mate with her.
link |
So a large number of experiments were done,
link |
but the first experiment really was to put the male mouse in
link |
with a female mouse who's in the so-called
link |
receptive phase of estrous.
link |
That is, she will allow mating.
link |
And he starts mating with her.
link |
And they go through the standard repertoire
link |
of mating behaviors that you observe in mice,
link |
mounting, thrusting, intromission,
link |
as it's called in the mouse sex world.
link |
Well, I guess, I don't know what the mice call it,
link |
but that's what the experimenters call it.
link |
And then afterwards that he will dismount, okay?
link |
So they observe this kind of mounting and sex behavior.
link |
It's very typical.
link |
But about halfway through the behavior,
link |
Dayu turned on the light to stimulate
link |
these estrogen receptor-containing neurons
link |
only in the male mouse.
link |
And what she observed was incredibly dramatic.
link |
The male mouse ceases from trying to mate
link |
with the female mouse and immediately tries
link |
to kill the female mouse.
link |
He starts attacking her.
link |
Then she turns off the light, the male stops,
link |
and goes back to trying to mate with the female mouse.
link |
I'm sure all of this was very confusing
link |
and disturbing to the female mouse.
link |
Nonetheless, that was the repertoire.
link |
She would stimulate these ventromedial hypothalamus neurons.
link |
The male mouse would immediately try and attack
link |
and kill the female mouse.
link |
And then she would stop the stimulation
link |
and he would stop trying to attack and kill the female mouse
link |
returned to the attempt at least
link |
to mate with the female mouse.
link |
These are such dramatic shifts in behavior
link |
triggered only by the activation
link |
of only the small set of neurons
link |
within the ventromedial hypothalamus.
link |
And for those of you that think that you can watch
link |
this sort of thing without being disturbed,
link |
I encourage you to go to YouTube.
link |
We will provide a link where you can see a video
link |
of this type of behavior.
link |
It's incredibly dramatic.
link |
The shift in behavior is almost instantaneous.
link |
It occurs within seconds, if not milliseconds,
link |
thousandths of a second.
link |
The next experiment that she did was to put a male mouse
link |
with this stimulation with light capability
link |
in its ventromedial hypothalamus into a cage alone,
link |
but with a rubber glove filled with air or water.
link |
Mouse is walking around sniffing, peeing,
link |
which is what male mice seem to do.
link |
They seem to urinate everywhere.
link |
Essentially an interesting, perhaps interesting feature
link |
of male mice and actually many male animals,
link |
perhaps even humans, we don't know, or maybe we do know.
link |
Basically, this has been observed time and time again
link |
in experiments, mainly by Lisa Stowers' lab
link |
at the Scripps Institute has characterized this.
link |
If you put female mice into an arena or a cage,
link |
they always urinate in a very small corner of that cage.
link |
Whereas if you put male mice into an arena or a cage,
link |
they urinate everywhere.
link |
They have this kind of obsession
link |
with spraying their urine everywhere.
link |
You can sort of transpose that
link |
to human behavior if you like.
link |
In any event, Dayu put the mouse in the cage alone,
link |
but with this rubber glove,
link |
the mouse is walking around urinating, et cetera,
link |
doing whatever it is that mice do.
link |
Then she stimulates the activation
link |
of these ventromedial hypothalamus neurons,
link |
and the mouse immediately tries to kill the glove.
link |
It goes into a rage attacking the glove
link |
as if it were another mouse or some other animate object,
link |
but of course it's an inanimate object.
link |
It's just a rubber glove.
link |
She stops the stimulation,
link |
and the mouse immediately goes back to being completely calm
link |
or at least not attacking.
link |
Again, we don't know what the mouse was feeling.
link |
So these are very dramatic videos.
link |
Again, you can see them by following the link
link |
that we'll provide in the caption.
link |
If that sort of thing is going to disturb you
link |
to see, for instance, one mouse attacking another,
link |
please just don't watch them.
link |
I'm not interested in traumatizing anybody,
link |
or you traumatizing yourself, that is.
link |
A number of different variations
link |
were done on this experiment.
link |
For instance, stimulating the VMH in female mice
link |
as opposed to male mice,
link |
putting the female mice in with other female mice
link |
or with other male mice,
link |
no matter what variation one carries out,
link |
so it doesn't matter if it's male with female,
link |
male with male, female with female, et cetera,
link |
stimulation of the ventromedial hypothalamus
link |
in a male mouse or a female mouse evokes
link |
this very dramatic, almost instantaneous,
link |
aggressive behavior, physically aggressive behavior.
link |
Subsequent experiments done by Dai-Yu Lin
link |
in her own laboratory and other laboratories
link |
have shown that the ventromedial hypothalamus
link |
is connected with a bunch of other brain areas
link |
that are interesting,
link |
and I'll talk about some of those in a little bit,
link |
but one of them that I want to call out now
link |
is the so-called PAG, the periaqueductal gray nucleus.
link |
This is a large structure in the back of the brain
link |
that houses things like neurons that can create opioids.
link |
We all know of the opioid crisis,
link |
but these are neurons that can produce endogenous means
link |
made by the body, chemicals that can cause pain relief.
link |
You could understand why that might occur
link |
in a circuit for aggression, right?
link |
Even if one is the aggressor,
link |
it's likely that they may incur some physical damage
link |
and they'd want some pain relief.
link |
The PAG also is connected to a number of neural circuits
link |
that eventually, through several processing stations,
link |
excuse me, arrive at things like the jaws,
link |
and in fact, stimulation of the ventromedial hypothalamus
link |
can evoke biting and aggressive biting behavior.
link |
Now, aggressive biting behavior is particularly interesting
link |
because in humans, and especially in human children,
link |
biting is something that,
link |
while young children might do as a form of aggression,
link |
tends to disappear pretty early in childhood,
link |
and if it doesn't, it's often seen as a mark of pathology.
link |
I have a story about this, actually.
link |
When I was a kid, I went to a summer sports camp,
link |
and I'll never forget this.
link |
We were playing soccer,
link |
and in a rare stroke of luck or accident,
link |
I happened to score a goal.
link |
I wasn't a particularly good soccer player,
link |
especially not at that stage in my life.
link |
They later figured out that it was just better
link |
to make me a fullback,
link |
because I could just wait there and do what fullbacks do.
link |
I was better at taking the ball or the person out
link |
than I was putting the ball in the goal.
link |
Nonetheless, I, again, by chance, I scored a goal,
link |
and I was trotting back to my side of the field,
link |
and all of a sudden, I felt this sting in my back.
link |
A kid, not to be named, although I do remember your name,
link |
I'm not going to tell you what his name was,
link |
a kid jumped on my back and bit me on the top of my back,
link |
and this, of course, resulted in a discussion
link |
and a timeout and all the usual things,
link |
and parents, I think, got involved.
link |
I didn't think much else of it,
link |
but I recall that this was considered
link |
especially troubling behavior,
link |
because he bit me as opposed to hit me
link |
or shoved me down or something of that sort,
link |
and it does seem as if the tendency to use biting
link |
as an aggressive behavior is associated
link |
with a more primitive circuitry.
link |
Now, here, I'm truly anthropomorphizing.
link |
I don't know what this other kid happened to be thinking
link |
or feeling at the time.
link |
And I certainly am not going to say that biting
link |
in every case reflects a pathology,
link |
although I think there is general agreement
link |
in the psychology community and the psychiatric community
link |
that past a certain age, the using of one's teeth
link |
to impart aggression and damage on others
link |
is a particularly primitive and troubling,
link |
or at least for the observer,
link |
the person that experiences a pretty disturbing event.
link |
Daew's lab has shown that activation
link |
of the ventromedial hypothalamus
link |
triggers a downstream circuit in the periaqueductal gray,
link |
which then triggers a whole other set of circuits
link |
of fixed action patterns.
link |
Here we are back to Lorenz again with fixed action patterns,
link |
including swinging of the limbs, right, punching.
link |
This wouldn't necessarily be controlled punching,
link |
but also biting behavior.
link |
So it's remarkable to me at least
link |
that we have circuits in our brain
link |
that can evoke violent use of things like our mouth
link |
or violent use of things like our limbs
link |
that of course could be used for things like singing
link |
or kissing or eating or gesticulating
link |
in any kind of polite or impolite way.
link |
The point here is that neural circuits,
link |
not individual brain areas,
link |
evoke the constellation of behaviors
link |
that we call aggression.
link |
Now, many of you are probably puzzled
link |
or at least should be
link |
because I've been talking about
link |
this highly specialized brain area,
link |
the ventromedial hypothalamus,
link |
and this highly specialized subcategory of neurons
link |
in the ventromedial hypothalamus,
link |
these neurons that make estrogen receptor.
link |
And yet the activation of those cells
link |
triggers dramatic and immediate aggression,
link |
both in males and in females
link |
and both against males and against females.
link |
So what's going on here?
link |
Most of us think about estrogen
link |
and we don't immediately think of aggression.
link |
Most of us hear testosterone
link |
and we might think about aggression,
link |
although other things as well.
link |
In order to understand this,
link |
I just want to briefly refer back to a conversation
link |
that I had on a previous episode
link |
of the Huberman Lab podcast
link |
and that was with my colleague,
link |
the great Robert Sapolsky,
link |
of course, as a professor at Stanford
link |
who studied testosterone and its impacts on behavior
link |
as well as estrogen and other hormones
link |
and their impacts on behavior.
link |
To make a long story short
link |
and to dispel a still unfortunately very common myth,
link |
testosterone does not increase aggressiveness.
link |
Testosterone increases proactivity
link |
and the willingness to lean into effort
link |
in competitive scenarios.
link |
Sometimes this is referred to as the challenge hypothesis,
link |
but to make a long story short,
link |
if people are given testosterone
link |
or if you look at people who have different levels,
link |
excuse me, of testosterone endogenously
link |
that they naturally make,
link |
what you'll find is that testosterone
link |
tends to increase competitiveness,
link |
but not just in aggressive scenarios.
link |
So if somebody is already aggressive,
link |
giving them testosterone will have the tendency
link |
to make them more aggressive.
link |
If somebody, however, is very benevolent and altruistic,
link |
giving them testosterone
link |
will make them more benevolent and altruistic,
link |
at least up to a point.
link |
Now, of course, there are certain forms
link |
of synthetic testosterone that are known
link |
in sports circles and in other circles
link |
to increase aggressiveness
link |
because of the way those particular forms
link |
of synthetic testosterone work.
link |
But in general, most of the experiments
link |
that I'm referring to have not been done using those.
link |
They've been done using the,
link |
let's call them the more traditional
link |
biological forms of testosterone
link |
or that resemble the biological forms of testosterone.
link |
In fact, Robert Sapolsky described
link |
a really interesting experiment
link |
in which if you look at testosterone levels
link |
or you administer additional testosterone
link |
to people who are doing philanthropy,
link |
giving money to organizations,
link |
and so they're essentially doing good
link |
because these are organizations doing good,
link |
what you find is that increased testosterone
link |
or further increasing testosterone
link |
makes people more willing to compete
link |
to give more money than the other person in the room
link |
in order to put it in air quotes,
link |
to alpha out the other person by giving more money.
link |
So this is an act of altruistic or benevolent philanthropy.
link |
It is not an act of aggression.
link |
Of course, we don't know what the people
link |
are feeling underneath all that.
link |
Again, we can't anthropomorphize
link |
or project onto other people what they're feeling.
link |
But the point is that testosterone itself
link |
does not make people more aggressive.
link |
And in the experiments that we've been talking about
link |
up until now, it's actually the activation
link |
of estrogen receptor containing neurons
link |
that makes these animals more aggressive.
link |
And it turns out there's evidence
link |
that in certain contexts,
link |
estrogen can make people more aggressive.
link |
So what's going on here?
link |
Well, what's going on is that
link |
testosterone can be converted into estrogen
link |
through a process called aromatization.
link |
There's an enzyme called aromatase.
link |
Anytime you have a word that ends in A-S-E,
link |
at least if it's in the context of biology,
link |
it's almost always, not always,
link |
but almost always an enzyme.
link |
So the aromatase enzyme converts testosterone into estrogen.
link |
And it is actually testosterone aromatized,
link |
converted into estrogen,
link |
and then binding to these estrogen-containing neurons
link |
in the ventromedial hypothalamus that triggers aggression.
link |
I want to repeat that.
link |
It is not testosterone itself that triggers aggression.
link |
It is testosterone aromatized into estrogen
link |
within the brain and binding to these estrogen receptor
link |
containing neurons in the ventromedial hypothalamus
link |
that evokes aggression and dramatic aggression at that.
link |
Now, this effect of estrogen causing aggression in the brain
link |
is very robust, so much so that if you take a mouse
link |
that lacks the aromatase enzyme
link |
or a human that lacks the aromatase enzyme,
link |
and they do exist,
link |
then there is a reduction in overall aggression
link |
despite high levels of testosterone.
link |
And if people who, or mice who have the aromatase enzyme
link |
have that enzyme blocked,
link |
well, then it doesn't matter
link |
how much you increase testosterone
link |
or any of its other derivatives.
link |
You do not observe this aggression.
link |
So this runs counter to everything that we know
link |
and think about the role of testosterone.
link |
Again, testosterone increases competitiveness.
link |
It can increase the desire to work under challenge.
link |
I've said it before, and I ran this or pressure tested this
link |
against Robert Sapolsky, who's been working on testosterone
link |
and its role in the brain and behavior for many decades now.
link |
It is fair to say that testosterone has the net effect
link |
of making effort feel good,
link |
or at least increasing the threshold
link |
at which effort feels bad or unsustainable.
link |
And it does that by way of changing the activity
link |
or the threshold for activation of brain structures
link |
like the amygdala and other brain structures
link |
associated with anxiety.
link |
So the next time somebody says
link |
testosterone makes people aggressive,
link |
you can say, ah, no, actually it's estrogen
link |
that makes people aggressive
link |
and animals aggressive for that matter.
link |
Now, of course, it is the case
link |
that because males have relatively less estrogen
link |
circulating in their brain and body than females, right?
link |
Because they have testes, not ovaries,
link |
that testosterone is required in the first place
link |
in order to be converted into estrogen
link |
to activate this aggressive circuit
link |
involving these estrogen receptor containing neurons
link |
in the ventromedial hypothalamus.
link |
But nonetheless, it is estrogen that is the final step.
link |
It is the hormone on which aggression hinges.
link |
And I think for most people,
link |
that's a quite surprising finding.
link |
And yet this is perhaps one of the more robust findings
link |
in both the animal and human literature
link |
as it relates to hormones
link |
and psychological states and behavior.
link |
Now, of course, it is the case that if testosterone is low,
link |
that a person or an animal
link |
will exhibit less aggressive behavior,
link |
but that's not because of reduced testosterone per se,
link |
it's because of the subsequent reduction in testosterone,
link |
meaning if there's no testosterone
link |
to aromatize into estrogen, estrogen will also be lower.
link |
So we've established that it's not testosterone,
link |
but testosterone converted into estrogen
link |
that activates these circuits for aggression.
link |
But nonetheless, it's still surprising, right?
link |
I mean, most of us don't think about estrogen
link |
as the hormone that stimulates aggression,
link |
but turns out it's all contextual.
link |
There are beautiful data
link |
showing that whether or not estrogen stimulates aggression
link |
can be powerfully modulated
link |
by whether or not days are short or days are long.
link |
In other words, whether or not
link |
there's a lot of sunshine or not.
link |
Now, obviously brain is encased in skull,
link |
so it doesn't really know
link |
if there's a lot of sunshine out there,
link |
even though you can see the sun with your eyes,
link |
you can feel it on your skin.
link |
Day length is converted into hormonal signals
link |
and chemical signals,
link |
and the primary hormonal and chemical signals
link |
involve melatonin and dopamine and also the stress hormones.
link |
So to make a very long story short,
link |
in the long days where we get a lot of sunlight,
link |
both in our eyes and on our skin,
link |
melatonin levels are reduced.
link |
Melatonin is a hormone
link |
that tends to produce states of sleepiness and quiescence.
link |
It also tends to activate pathways
link |
that tend to reduce things like breeding
link |
and sexual behavior.
link |
In long days, dopamine is increased.
link |
Dopamine is a molecule associated
link |
with feelings of wellbeing and motivation,
link |
and the desire to seek out all sorts of things,
link |
all sorts of motivated behaviors.
link |
provided we're getting enough sunlight on our skin
link |
the stress hormones, especially cortisol
link |
and some of the other stress hormones
link |
are reduced in levels.
link |
If estrogen levels are increased experimentally
link |
under long day conditions,
link |
it does not evoke aggression.
link |
However, in short days, if estrogen is increased,
link |
there's a heightened predisposition for aggression.
link |
And that makes perfect sense
link |
if you think about what short days do
link |
to the biology of your brain and body.
link |
In short days, the melatonin signal goes up.
link |
There's more melatonin circulating
link |
for more of each 24 hour cycle.
link |
Stress hormones are circulating more.
link |
Short days tend to be associated with winter.
link |
In winter, we are bombarded with more bacteria and viruses
link |
because bacteria and viruses actually survive better
link |
in cold than they do in heat.
link |
In fact, in my laboratory,
link |
we work with a lot of viruses and bacteria
link |
and when we want to keep them alive,
link |
we put them in the freezer.
link |
If we want to kill them, if we want to inoculate them,
link |
we put them under UV light
link |
like you would see from the sunlight.
link |
So shorter days are conducive to aggression,
link |
not because days are short per se,
link |
but because stress hormone levels are higher
link |
and because dopamine levels are lower.
link |
Now here's where all of this starts to converge
link |
on a very clear biological picture,
link |
a very clear psychological picture,
link |
and indeed a very clear set of tools
link |
that we can think about and use.
link |
Under conditions where cortisol is high,
link |
where the stress hormone is elevated,
link |
and under conditions where the neuromodulator serotonin
link |
is reduced, there is a greater propensity
link |
for estrogen to trigger aggression.
link |
Now, again, I know I've said it before,
link |
but for males who make a lot of testosterone
link |
relative to estrogen, you have to swap in your mind
link |
this idea that if testosterone is high,
link |
that means that estrogen is low
link |
because while that can be true in the periphery in the body,
link |
if testosterone is high,
link |
there is going to be some aromatization,
link |
that conversion of testosterone to estrogen.
link |
So anytime you hear that testosterone is high,
link |
you should think testosterone is high in the body
link |
and perhaps estrogen is low in the body,
link |
but that means that there's going to be heightened levels
link |
of estrogen in the brain
link |
and therefore increased propensity for aggression.
link |
In females who generally make less testosterone
link |
relative to estrogen,
link |
there is sufficient estrogen already present
link |
to trigger aggression.
link |
So both males and females are primed for aggression,
link |
but that's riding on a context
link |
and that context of whether or not you get a tendency
link |
for aggression or not
link |
depends on whether or not cortisol is high or low
link |
and I'm telling you that if cortisol is relatively higher
link |
in any individual, there's going to be a tilt,
link |
an increase in that hydraulic pressure
link |
that Lorenz talked about toward aggression.
link |
And if serotonin, the neuromodulator
link |
that is associated with feelings of wellbeing
link |
and sometimes even of slight passivity,
link |
but certainly of wellbeing, if serotonin is low,
link |
there's also going to be a further shift
link |
towards an aggressive tendency.
link |
So if we return to Lorenz's hydraulic pressure model
link |
of aggression and other internal states,
link |
we realize that external stimuli,
link |
things that we hear, things that we see,
link |
for instance, someone saying something upsetting
link |
or us seeing somebody do something
link |
that we don't like to others or to us,
link |
as well as our internal state,
link |
our subjective feelings of wellbeing,
link |
but also our stress level,
link |
our feelings of whether or not we have enough resources
link |
and are content with what we have,
link |
all of that is converging on this thing
link |
that we call internal state and creating this pressure
link |
of either to be more aggressive or less aggressive.
link |
And now we have some major players
link |
feeding into that final pathway,
link |
that question of whether or not
link |
will we hit the other person?
link |
Will we say the thing that is considered aggressive?
link |
Will we not say it?
link |
If somebody says something or does something aggressive
link |
to us, will we respond or will we be submissive
link |
Again, there are many things funneling into that question
link |
and dictating whether or not the answer is,
link |
absolutely, I'll fight back,
link |
or I'm going to attack them even unprovoked,
link |
or if they say this, I'm going to do that,
link |
or no matter what they do, I'm not going to respond.
link |
These kinds of things are very complex
link |
and yet we really can boil them down
link |
to just a few common elements.
link |
And I'm telling you that those elements
link |
are whether or not cortisol levels are relatively lower
link |
or relatively higher.
link |
Again, relatively higher is going to tend
link |
to make people more reactive, why?
link |
Because reactivity is really a function
link |
of the autonomic nervous system,
link |
which is sort of like a seesaw that oscillates
link |
between the so-called sympathetic arm
link |
of the autonomic nervous system,
link |
which tends to put us into a state of readiness
link |
through the release of adrenaline.
link |
Cortisol and adrenaline,
link |
when they're circulating in the brain and body,
link |
make us more likely to move and to react and to speak.
link |
It's actually what will induce a kind of low-level tremor,
link |
which is an anticipatory tremor
link |
to be able to move more quickly, right?
link |
A body in motion is more easily set into further motion,
link |
And the neuromodulator serotonin is a neuromodulator
link |
that in general is associated with feelings of wellbeing
link |
in response to what we already have.
link |
So when we are well-fed,
link |
serotonin tends to be released in our brain and body,
link |
in particular, well-fed with carbohydrates.
link |
The precursor to serotonin is tryptophan.
link |
And indeed, there are nice studies exploring
link |
the types of diets, nutritional programs,
link |
that can reduce aggressive behavior,
link |
both in children and in adults.
link |
And tryptophan-rich diets or supplementation with tryptophan.
link |
So for tryptophan-rich diets, things like white turkey meat,
link |
but then there are also a number of carbohydrates.
link |
You can look up, it's very easy to find,
link |
foods that contain lots of tryptophan.
link |
Those foods contain the precursor to serotonin.
link |
Now, it isn't simply the case that eating more foods
link |
with tryptophan will tend to reduce your aggression.
link |
I suppose it could do that if you ate it in abundance,
link |
it could make you tired,
link |
and then you're less likely to be aggressive.
link |
I don't recommend that strategy.
link |
But the idea here is that when it's been explored,
link |
increasing levels of tryptophan,
link |
either by supplementation or by food,
link |
or drugs, prescription drugs that increase serotonin,
link |
so for instance, fluoxetine, sometimes called Prozac
link |
or Zoloft or any number of the other SSRIs,
link |
tend to reduce aggressive behavior.
link |
Now, not always, but in general, that's the case.
link |
Similarly, because elevated cortisol
link |
tends to shift the whole system,
link |
again, create more of a hydraulic pressure
link |
towards aggressive states.
link |
If cortisol levels are reduced,
link |
well, then the tendency for aggressive behavior is reduced.
link |
This is supported by a number of peer-reviewed studies.
link |
We'll provide links to some of those
link |
in the caption show notes.
link |
And we're going to return to these a bit later
link |
in the context of specific studies
link |
that have looked at genetic variants
link |
in different individuals that cause them
link |
to make more or less serotonin,
link |
or at least to metabolize serotonin differently.
link |
This is also the case for so-called
link |
intermittent explosive disorder
link |
that can often be associated with gene variants
link |
that control how much serotonin is made
link |
or how it's metabolized or how much cortisol is made
link |
and how much it's metabolized.
link |
In thinking about tools,
link |
there are a number of things that one could consider.
link |
First of all, there are a number of decent studies
link |
exploring how supplementation with the omega-3 fatty acids,
link |
which are precursors of some of the transmitter systems,
link |
including serotonin, that can modulate,
link |
not directly mediate, but modulate mood and emotional tone.
link |
Supplementation with the omega-3s
link |
has been shown to reduce impulsivity and aggressiveness
link |
in certain contexts, in things like ADHD
link |
or in individuals who have a predisposition
link |
for aggressive type behavior or aggressive thinking.
link |
Now, that doesn't necessarily mean
link |
that the omega-3 fatty acids are going directly
link |
to the ventromedial hypothalamus
link |
and changing the activity of neurons there.
link |
More likely, they are causing or modulating
link |
an overall shift in mood through the immune system,
link |
through hormone systems that are changing the overall tone
link |
or the propensity for neurons
link |
in the ventromedial hypothalamus to be activated.
link |
How much omega-3 fatty acid, what source?
link |
Well, we've talked about this on the podcast before.
link |
You can, of course, get omega-3 fatty acids
link |
from a number of different foods.
link |
Getting them from whole foods
link |
is probably the best way to do it.
link |
But many people, including people with depression,
link |
will often supplement with one gram or more
link |
of omega-3 fatty acids per day.
link |
Some people, including myself, will take them every day
link |
as just a general mood enhancer.
link |
I don't suffer from depression,
link |
but I've found it to be beneficial for my health.
link |
And so some people will do that.
link |
And I've talked about before
link |
how in double-blind placebo-controlled studies,
link |
people taking one to three grams of omega-3 fatty acids
link |
per day, typically in the form of a high-quality fish oil,
link |
although there are other sources as well,
link |
algae and so forth,
link |
can experience improvements in mood
link |
that are on par with some of the SSRIs,
link |
the selective serotonin reuptake inhibitors.
link |
And of course, if you are prescribed an SSRI
link |
by your psychiatrist or other doctor,
link |
please do take that and don't cease to take it,
link |
just simply to take omega-3s.
link |
However, you might mention to them,
link |
and you can find links to the studies
link |
in our previous episodes on depression,
link |
that supplementation with omega-3 fatty acids
link |
at this one gram or more of EPA specifically,
link |
so getting above that one gram threshold
link |
as high as three grams per day of the EPA
link |
has allowed people to take lower doses of SSRIs
link |
and still keep their mood in a place
link |
that's beneficial for them.
link |
And in terms of keeping cortisol in a range
link |
that's healthy and doesn't bias someone
link |
toward high levels of aggression and irritability,
link |
that's again going to be set
link |
by a number of larger modulators or contextual cues.
link |
And I've talked about some of those on the podcast,
link |
but I'll just briefly recap them now.
link |
Obviously getting sunlight in your eyes early in the day
link |
and as much sunlight as you safely can in your eyes
link |
throughout the day is going to be important.
link |
Again, because of this effect of estrogen in long days,
link |
not increasing aggression.
link |
However, in shorter days, estrogen increases aggression
link |
because of the increase in cortisol observed in short days.
link |
Another way to reduce cortisol was discussed
link |
in our episode on heat and the use of sauna and heat,
link |
but also hot baths.
link |
It turns out that hot baths and sauna
link |
can be very beneficial for reducing cortisol.
link |
All the details on that are included
link |
in the episode on heat and its timestamp,
link |
so you can go directly to that
link |
if you want to learn about the temperatures
link |
and the various durations,
link |
but to just give a synopsis of that,
link |
a 20 minute sauna at anywhere from 80 to 100 degrees Celsius
link |
is going to be beneficial for reducing cortisol.
link |
If you don't have access to a sauna,
link |
you could do a hot bath,
link |
adjust the temperature so you don't burn yourself.
link |
I think 80 to 100 degrees Celsius is going to be too hot
link |
for many people if it's a hot bath,
link |
whereas many people who can't tolerate that hot bath
link |
can tolerate the sauna.
link |
So safety first, always, and of course,
link |
but hot baths reduce cortisol.
link |
Hot saunas reduce cortisol of a duration
link |
about 20 or 30 minutes is going to be beneficial.
link |
And of course, some of you may be interested
link |
in exploring the supplementation route
link |
and for reductions in cortisol,
link |
really the chief player there is ashwagandha,
link |
which is known to decrease cortisol fairly potently.
link |
I should just warn you that if you're going to use
link |
ashwagandha in order to reduce cortisol,
link |
first of all, check with your doctor or healthcare provider
link |
before adding or subtracting anything
link |
from your supplementation or health regimen.
link |
Of course, I don't just say that to protect us.
link |
I say that to protect you.
link |
You are responsible for your health,
link |
what you take and what you don't take.
link |
Chronic supplementation with ashwagandha
link |
can have some not so great effects of disruption
link |
of other hormone pathways and neurotransmitter pathways.
link |
So the limit seems to be about two weeks of regular use
link |
before you'd want to take a break of about two weeks.
link |
So ashwagandha, again, a very potent inhibitor of cortisol,
link |
but with some other effects as well,
link |
don't use it chronically for longer than two weeks.
link |
But if your goal is to reduce cortisol,
link |
let's say you're going through a period
link |
of increased irritability and aggressive tendency,
link |
maybe you're also not getting as much light
link |
as you would like, and perhaps also
link |
if there are other circumstantial things
link |
leading you towards more aggressiveness
link |
and your goal is to reduce aggressiveness,
link |
that can be potentially helpful.
link |
And in light of all this stuff about cortisol
link |
and estrogen and day length,
link |
I should mention that there are in fact some people
link |
who have a genetic predisposition
link |
to be more irritable and aggressive.
link |
There are a couple of different gene pathways
link |
associated with this.
link |
We never like to think about just one gene
link |
causing a specific behavior.
link |
The way to think about genes is that genes generally code
link |
for things within our biology,
link |
in the context of today's discussion,
link |
things like neural circuits
link |
or the amounts of neurotransmitters that are made
link |
or the amounts of hormones that are made
link |
or the amount of neurotransmitter hormone receptors
link |
or enzymes, et cetera,
link |
that shift the activity of our biology
link |
in a particular direction, they bias our biology.
link |
And in fact, there is a genetic variant
link |
present in certain people
link |
that adjusts their estrogen receptor sensitivity
link |
and that estrogen receptor sensitivity
link |
can result in increased levels of aggression,
link |
sometimes dramatic increases.
link |
However, and also very interestingly,
link |
photoperiod, meaning day length,
link |
is a strong modulator of whether or not
link |
that aggressiveness turns up or not.
link |
Whether or not that person with the particular gene variant
link |
is more aggressive or not depends on how long the day is
link |
and how long the night is.
link |
One particular study that I like that references this
link |
is Trainor et al, the title of the study is
link |
photoperiod reverses the effects of estrogens
link |
on male aggression via genomic and non-genomic pathways.
link |
This was a paper published in the Proceedings
link |
of the National Academy of Sciences.
link |
We'll put a reference to this in the show notes
link |
if you'd like to explore it further.
link |
But it really points to the fact that rarely,
link |
sometimes, but rarely is it the case
link |
that just one gene will cause somebody
link |
to be hyper aggressive.
link |
Almost always, there's going to be an interplay
link |
between genetics and environment
link |
and as environment changes, such as day length changes
link |
and the length of night changes,
link |
so too will the tendency for people with a given
link |
genetic variant to be more aggressive or not.
link |
Now, of course, in the absence of detailed genetic testing
link |
for this particular estrogen receptor variant,
link |
most people, I'm guessing you,
link |
are probably not walking around knowing
link |
that you have this gene or not.
link |
Regardless, I think it's important to pay attention
link |
to how you feel at different times of year,
link |
depending on whether or not it's summer,
link |
whether or not it's winter,
link |
whether or not you're getting sufficient sunlight,
link |
meaning viewing sufficient sunlight or not,
link |
whether or not you're getting sufficient sunlight exposure
link |
to your skin or not,
link |
whether or not you're indoors all the time.
link |
Generally, those things correlate with season,
link |
You can go through long bouts of hard work
link |
in the summer months when days are long,
link |
but you're indoors a lot and getting a lot
link |
of fluorescent light exposure late in the evening,
link |
and perhaps that's when you're feeling more aggressive.
link |
So we have to be careful about drawing
link |
a one-to-one relationship between any biological feature
link |
and certainly psychological or behavioral feature
link |
like aggressiveness, but it's, I believe,
link |
helpful to know that these genetic biases exist,
link |
how they play out.
link |
Again, they shift our biology
link |
in a general thematic direction.
link |
They don't change one thing.
link |
They change a variety of things that bias us toward
link |
or away from certain psychological and behavioral outcomes
link |
and the various things that we can do
link |
in order to offset them.
link |
We described those earlier in terms of trying
link |
to keep cortisol low by getting sufficient sunlight
link |
regardless of time of year and regardless of whether
link |
or not you happen to have this particular genetic variant.
link |
So earlier I talked about how it is testosterone converted
link |
into estrogen that's activating aggression
link |
in the ventromedial hypothalamus, not testosterone itself.
link |
However, there are some studies carried out in humans
link |
that have evaluated the effects of testosterone
link |
and how levels of testosterone correlate
link |
with aggressiveness in the short term.
link |
I'm just going to detail a few of those studies
link |
because I think they are interesting and important.
link |
First of all, there is a study that has explored levels
link |
of testosterone in men of different professions.
link |
Now, before I tell you the data,
link |
I want to be very clear here.
link |
With a study such as this, one never knows whether
link |
or not these men went into a particular profession
link |
because they had a testosterone level of a given value
link |
or whether or not the work itself altered
link |
their testosterone levels or both.
link |
And I think it's fair to assume that it's probably both.
link |
So be very careful in assuming
link |
that a given testosterone level is causal
link |
for choosing a particular career
link |
or that a particular career is causal
link |
for creating a particular testosterone level.
link |
This study used salivary testosterone levels
link |
as the measure, which to be fair,
link |
is not the best way to measure testosterone.
link |
Typically blood draw would be the best way
link |
to measure testosterone, but nonetheless,
link |
provided the appropriate methods are used,
link |
salivary testosterone can be a reasonable measure
link |
The different occupations that were looked at were,
link |
and here they just looked at men in this particular study,
link |
were ministers, salesmen,
link |
they didn't say what particular types of salesmen,
link |
firemen, professors of all things,
link |
physicians and NFL players.
link |
And what they discovered was that the testosterone levels
link |
were essentially in that order from low to highest.
link |
So minister, salesman, fireman, professor,
link |
physician, NFL player.
link |
Now we could micro dissect all the different stereotypes
link |
and all the different features of each of these jobs.
link |
For instance, we don't know whether or not the fact
link |
that the fireman happened, at least in this study,
link |
to have lower testosterone levels on average
link |
than the professors or the physicians
link |
was because firemen have lower testosterone levels
link |
or because they have a much more stressful job
link |
and their cortisol levels are higher
link |
than the professor or the physician
link |
and cortisol and testosterone, not always,
link |
but generally are in somewhat antagonistic push-pull mode
link |
because they derive from the same precursor, et cetera.
link |
Typically when cortisol is high,
link |
testosterone tends to be lower and vice versa.
link |
So we don't know what's causing these effects.
link |
And again, this is just one study and just six occupations,
link |
but I think it's relatively interesting
link |
given the fact that each of these professions
link |
involves different levels of competitiveness, right?
link |
So we don't necessarily just want to think about the level
link |
of physical exertion that's required,
link |
but also the level of competitiveness
link |
because it's known that competitive interactions
link |
can cause increases in testosterone,
link |
in particular in the winners of competitive interactions,
link |
a topic for a future podcast.
link |
Meanwhile, studies that have analyzed
link |
also again salivary testosterone in prisoners,
link |
in this case, female prisoners,
link |
so these are incarcerated individuals,
link |
have looked at levels of testosterone
link |
according to whether or not the person committed
link |
a nonviolent or a violent crime
link |
in order to arrive in prison,
link |
and higher levels of salivary testosterone
link |
were related to those that had arrived in prison
link |
because of conviction of a violent crime
link |
as opposed to a nonviolent crime.
link |
Likewise, when they analyze prison rule violations,
link |
so an indirect measure of aggressiveness,
link |
but in this case, it was strongly associated
link |
with aggressiveness because they knew
link |
what the violations were,
link |
they found were for prisoners that had none,
link |
no prison violations, prison rule violations,
link |
I should say their testosterone levels tended to be lower
link |
than the testosterone levels of women that had some,
link |
even one or more aggressive violations of prison rules.
link |
We'll provide links to these studies in the show notes
link |
if you'd like to go into them further.
link |
Obviously studies like this need to be taken
link |
with a grain of salt because there are so many
link |
different factors, different prisons have different degrees
link |
of violence to begin with and competitiveness to begin with.
link |
But just as a final pass at examining the role
link |
between testosterone and aggressiveness,
link |
there was a very interesting study from Gotz et al.
link |
G-O-E-T-Z published in 2014 that looked at serum,
link |
so in this case, blood levels of testosterone,
link |
30 minutes after application of a gel-based testosterone
link |
that goes transdermal so that the testosterone
link |
can go very quickly into the bloodstream
link |
and then did brain imaging to evaluate the activity
link |
of neurons in the so-called corticomedial amygdala.
link |
The medial amygdala is one of the areas
link |
of the amygdala complex as we call it because it's complex,
link |
it's got a lot of different nuclei,
link |
you now know what nuclei are, little clusters of neurons,
link |
it's got a lot of different ones,
link |
but that medial and that corticomedial amygdala
link |
in particular is known to be associated
link |
with aggressive type behaviors.
link |
It's linked up with, it's part of the larger circuit
link |
that includes the ventromedial hypothalamus
link |
and other brain areas that we referred to earlier,
link |
What is remarkable about this study is that it showed
link |
that just 30 minutes after application
link |
of this so-called androgel,
link |
this testosterone that seeps into the bloodstream,
link |
there was a significant increase in, of course,
link |
testosterone and corticomedial amygdala activation.
link |
So testosterone can have acute effects,
link |
immediate effects on the pathways related to aggression.
link |
And I think this is something that's not often discussed
link |
because many of the effects of steroid hormones
link |
like testosterone and estrogen are very slow acting.
link |
In fact, steroid hormones,
link |
because they have a certain biochemical composition,
link |
can actually pass through the membranes of cells,
link |
so the outside of a cell and into the nucleus of the cell
link |
and change gene expression in the cell.
link |
Think about puberty, the kid that goes home for the summer
link |
and then comes back looking completely different.
link |
Well, that's because a lot of genes got turned on
link |
by steroid hormones like testosterone and estrogen,
link |
but the steroid hormones can also have
link |
very fast acting effects.
link |
And with testosterone in particular,
link |
those can be remarkably fast acting.
link |
And one of the most apparent
link |
and well-documented fast acting effects is this effect,
link |
the ability to activate cells within the amygdala.
link |
So you might say, well,
link |
I thought the amygdala was associated with fear,
link |
wouldn't testosterone then cause fear?
link |
No, turns out that the amygdala harbors both cortisol,
link |
corticosterone receptors, and testosterone receptors,
link |
and they each adjust the activity
link |
in the amygdala differently,
link |
such that testosterone tends to activate amygdala circuitry
link |
for inducing states of mind and body
link |
that are more action-based.
link |
And indeed in animals and in humans,
link |
testosterone application and activation
link |
of this corticomedial amygdala pathway
link |
will make animals and humans lean into effort.
link |
This is why I say testosterone makes effort feel good,
link |
or at least biases the organism
link |
toward leaning into challenge.
link |
So if you recall, there's not just one type of aggression,
link |
there's reactive aggression,
link |
which is triggered when one is confronted with something
link |
that sometimes is inevitable, right?
link |
One needs to fight for their life
link |
or for somebody else's life,
link |
but also proactive aggression.
link |
And proactive aggression involves activation
link |
of those go pathways in the basal ganglia
link |
and a leaning into effort to overcome
link |
whatever state one happens to be in to begin with.
link |
And so this is very important because it points to the fact
link |
that yes, estrogen is activating aggression pathways
link |
that are in the ventromedial hypothalamus,
link |
but it's very likely the case
link |
that testosterone is acting to accelerate
link |
or to bias states of mind and body
link |
toward those that will lead to aggression.
link |
Again, aggression is not like a switch on and off,
link |
it's a process, it has a beginning, a middle, and an end.
link |
Remember that hydraulic pressure
link |
that Konrad Lorenz hypothesized?
link |
Well, think of testosterone as increasing the pressure
link |
toward an aggressive episode
link |
and then estrogen actually triggering
link |
that aggressive episode in the ventromedial hypothalamus.
link |
So if somebody tells you that testosterone,
link |
endogenous or exogenous, makes people aggressive,
link |
Testosterone tends to make people lean into effort
link |
and if that effort involves being aggressive,
link |
either reactively aggressive or proactively aggressive,
link |
well, then it will indeed lead to aggression,
link |
but the actual aggression itself
link |
is triggered by estrogen, not testosterone.
link |
Now, thus far, we really haven't talked too much
link |
about the social context in which aggression occurs
link |
and that's because there is a near infinite,
link |
if not infinite number of variables that will determine that.
link |
So for instance, violent aggression is entirely appropriate
link |
at a professional boxing match
link |
provided it's occurring inside the ring
link |
and only between the competitors
link |
and within the bounds of the rules of the sport, et cetera.
link |
However, there are some things
link |
that tend to bias certain social contexts
link |
toward being more aggressive or less aggressive
link |
and not always physical aggression
link |
and those generally come in two forms
link |
that many of you are familiar with,
link |
which are alcohol and caffeine.
link |
Let's discuss caffeine first.
link |
Why would caffeine increase aggressive impulsivity?
link |
Well, the general effects of caffeine
link |
are to increase autonomic arousal,
link |
the activity of the so-called sympathetic arm
link |
of the autonomic nervous system,
link |
which is, to put it very much in plain language,
link |
it's the alertness arm of your nervous system.
link |
That is, it creates a sense of readiness
link |
in your brain and body
link |
and it does so by activating
link |
the so-called sympathetic chain ganglia.
link |
Again, as I always remind people,
link |
simpa and sympathetic does not mean sympathy.
link |
Simpa means together or all at once
link |
and caffeine tends to bias our brain and body
link |
to activate the sympathetic chain ganglia,
link |
which run from about the base of your neck
link |
until the top of your pelvis
link |
and deploy a bunch of chemicals
link |
that jut out into the rest of your body,
link |
activate adrenaline release.
link |
There's a parallel increase of adrenaline in your brain,
link |
creating the state of alertness and readiness.
link |
That state of alertness and readiness
link |
can be for all sorts of things, not just aggression.
link |
However, when we are in a state
link |
of increased sympathetic tone, meaning more alert,
link |
such as after drinking caffeine,
link |
we will bias all those brain and body systems,
link |
the hormones, the chemicals, et cetera,
link |
that exist toward action as opposed to inaction.
link |
So put simply, caffeine can increase impulsivity.
link |
No surprise there.
link |
On the opposite end of things,
link |
alcohol tends to decrease activity
link |
in the sympathetic arm of the autonomic nervous system,
link |
tends to make us feel less alert.
link |
Now, initially it can create a state of alertness
link |
because of its effects in inhibiting the forebrain.
link |
Our forebrain prefrontal cortex in particular
link |
has what's called top-down inhibition.
link |
It exerts a inhibitory or a quieting effect
link |
on some of the circuits of the hypothalamus,
link |
such as the ventromedial hypothalamus.
link |
The way to conceptualize this is that your forebrain
link |
is able to rationalize and think clearly
link |
and to suppress behavior and to engage the no-go pathways,
link |
telling you don't say that mean thing,
link |
don't do that violent thing, et cetera.
link |
Alcohol initially tends to increase
link |
our level of overall activity by reducing inhibition,
link |
not just in that forebrain circuit,
link |
but in other circuits, tends to make us more active.
link |
We tend to talk more than we normally would,
link |
move more than we normally would,
link |
but very shortly thereafter starts acting as a sedative
link |
by way of reducing activity in the forebrain,
link |
releasing some of the deeper brain circuits
link |
that are involved in impulsivity,
link |
but also causing a somewhat sedative effect.
link |
And then of course, as alcohol levels increase even further,
link |
people eventually will pass out, blackout, et cetera.
link |
So what we've got with alcohol and caffeine
link |
is we've got two opposite ends of the spectrum,
link |
caffeine increasing arousal and readiness
link |
and the tendency for impulsivity,
link |
and alcohol also increasing impulsivity,
link |
but through a different mechanism.
link |
A really interesting study,
link |
and I should just mention that the title of the study
link |
is caffeinated and non-caffeinated alcohol use
link |
and indirect aggression, the impact of self-regulation.
link |
So the title is almost self-explanatory.
link |
This was a paper published in the Journal
link |
of Addictive Behavior in 2016,
link |
examining how ingestion of alcohol
link |
that's either caffeinated or non-caffeinated alcohol drinks
link |
impacted what they call indirect aggression.
link |
And just to remind you what indirect aggression is,
link |
these are not physical acts of aggression,
link |
these are verbal acts of aggression.
link |
So embarrassing others or otherwise somehow
link |
trying to reduce the wellbeing of others
link |
by saying certain things in particular in groups.
link |
This study examined both males and females.
link |
This was done by way of a college campus study.
link |
Subjects were 18 to 47 years old.
link |
I guess there's some older students on that campus,
link |
or maybe they use some non-students,
link |
but these days you've also got some students
link |
that are in their 30s and 40s.
link |
So they have a fairly broad swath of subjects included,
link |
fairly broad racial background as well,
link |
included not at equal numbers,
link |
but at least they included a pretty broad spectrum
link |
of people with different backgrounds.
link |
They looked in particular at people
link |
that ingested non-caffeinated alcohol drinks
link |
at a frequency of 9.18 drinks per week.
link |
Okay, again, this is a college campus,
link |
not that I encourage that.
link |
I'm one of these people that I've never really liked,
link |
drugs or alcohol, and it's sort of fortunate in that way,
link |
I can drink or not drink and tend to not drink.
link |
But so to me, 9.18 drinks per week sounds like a lot,
link |
but I know for some people that might actually be typical.
link |
And then others who were drinking
link |
at least one caffeinated alcoholic beverage per week,
link |
and those individuals end as high, I should say,
link |
as 7.87 caffeinated alcohol beverages per week.
link |
So this would be energy drinks
link |
combined typically with hard alcohol.
link |
That's fairly commonly available in bars and so forth.
link |
And some individuals drank as much as, goodness,
link |
20.36 alcoholic drinks per week total,
link |
some that were caffeinated, some that were not caffeinated.
link |
The basic outcome of this study
link |
was that the more alcohol someone tended to consume,
link |
the more likely it was that they would engage
link |
in these indirect aggressive type behaviors.
link |
And in terms of the caffeinated alcoholic beverages,
link |
there the effect was especially interesting.
link |
Here I'm just going to paraphrase,
link |
or I'll actually read from the study.
link |
Quote, with regard to caffeinated alcoholic beverage use,
link |
our findings indicated
link |
that heavier caffeinated alcohol beverage use
link |
was associated positively with indirect aggression
link |
even after considering one's typical alcohol use
link |
and dispositional aggression.
link |
What this means is that even though alcohol
link |
can bias certain individuals to be more aggressive,
link |
and even though certain individuals
link |
already have a disposition toward being more aggressive,
link |
there was an effect that was independent,
link |
meaning above and beyond both alcohol and a predisposition,
link |
meaning if someone was consuming
link |
caffeinated alcoholic beverages,
link |
they had a particularly high likelihood
link |
of engaging in indirect aggressive behavior.
link |
Now, this makes perfect sense
link |
in light of the model they propose,
link |
which is this self-regulation model
link |
that basically self-regulation involves several things.
link |
It involves engaging in certain behaviors
link |
and suppressing other behaviors.
link |
So as described before,
link |
because alcohol tends to have a sedative,
link |
suppressive effect on the autonomic nervous system,
link |
at least after the initial period,
link |
it's going to tend to reduce the likelihood
link |
that people will engage in any type of behavior,
link |
whereas caffeine will increase autonomic arousal
link |
and increase the likelihood that someone will engage
link |
in a particular type of behavior, aggressive or otherwise.
link |
So the combination of caffeine and alcohol
link |
is really acting as a two-prong system
link |
to bias people towards more impulsivity,
link |
that is less self-regulation.
link |
So it's really yanking your volitional control,
link |
your ability to engage in prefrontal top-down inhibition
link |
over your hypothalamus
link |
from two distinct and specific circuits.
link |
By now, you should be getting the impression
link |
that self-regulation is a key feature
link |
of whether or not somebody, maybe even you,
link |
is going to engage in aggressive speech
link |
or aggressive behavior.
link |
And we've talked about a number of tools
link |
that one can use to reduce the probability
link |
that that will happen.
link |
I suppose if the context were appropriate,
link |
you could even take those two recommendations
link |
and just invert them and increase the likelihood
link |
that aggressiveness would have happened.
link |
But regardless, self-regulation is key.
link |
And in light of that, I want to share with you a study
link |
that's focused on kids,
link |
but that has important ramifications for adults as well.
link |
As you probably are already aware,
link |
there are many kids out there that suffer
link |
from so-called attention deficit hyperactivity disorder,
link |
There are also many adults we are finding
link |
that are suffering from ADHD.
link |
And there's also an epidemic, I would say,
link |
of people that are concerned about
link |
whether or not they have ADHD.
link |
Now, whether or not they have true clinical ADHD or not
link |
We did an episode all about ADHD and tools for ADHD.
link |
I would encourage you to check out that episode
link |
and some of the diagnostic criteria.
link |
If you have the opportunity,
link |
you can find that at hubermanlab.com.
link |
As this study I'm about to share with you aptly points out,
link |
there is no objective diagnostic marker of ADHD.
link |
There's no biomarker or blood draw or blood test for ADHD.
link |
Whether or not one has ADHD depends on their performance
link |
on a number of different cognitive tests
link |
and behavioral tests and self-report.
link |
In any event, the study I'm about to share with you
link |
explored how a particular pattern of supplementation
link |
in kids with ADHD was able to reduce aggressive episodes
link |
and impulsivity and increase self-regulation.
link |
And the title of the study is efficacy of carnitine
link |
in the treatment of children
link |
with attention deficit hyperactivity disorder,
link |
even though they put carnitine in the title,
link |
that what they focused on was
link |
whether or not acetyl-L-carnitine supplementation
link |
could somehow adjust the behavioral tendency
link |
of these kids with ADHD.
link |
And to make a long story short, indeed it did.
link |
There was a very significant effect
link |
of acetyl-carnitine supplementation
link |
on improving some of the symptomology of ADHD.
link |
A few details about this study
link |
that might be relevant to you.
link |
This was a randomized double blind placebo controlled
link |
double crossover study.
link |
This was done as an outpatient study
link |
so the kids weren't in a hospital.
link |
They were living out in the world.
link |
This again was done on younger kids.
link |
So this was six to 13-year-old kids
link |
that were diagnosed with ADHD.
link |
They received either acetyl-L-carnitine or placebo,
link |
and they did all the good practice stuff
link |
that good researchers do of making sure that the placebo
link |
and the acetyl-L-carnitine had similar look and taste.
link |
It was consumed twice daily after meals.
link |
Now she just mentioned that acetyl-L-carnitine
link |
typically is taken in capsule form
link |
or occasionally an injectable form here.
link |
They were using this as a drink,
link |
which is essentially the same as capsule form,
link |
but the powder is just going directly into liquid.
link |
And the carnitine dosage was 100 milligrams per kilogram.
link |
So they're doing this according to the body weight
link |
of these kids with a maximum dosage of four grams per day.
link |
The quantity of the medication was supplied.
link |
Here I'm reading for a period of eight weeks,
link |
and every eight weeks,
link |
a new quantity of medication was supplied.
link |
So basically this is a fairly long-term study
link |
exploring behavioral outcomes and psychological outcomes
link |
in week eight, 16, and 24.
link |
They also looked at things
link |
that you could only get through a blood draw.
link |
So things like hemoglobin, hematocrit,
link |
red blood cell count, white blood cell count, et cetera.
link |
These are kids, and even if it were adults,
link |
they were quite appropriately examining
link |
a lot of the physiological measures
link |
that one would want to carry out to make sure,
link |
first of all, that blood levels of carnitine are increasing,
link |
and indeed they confirm that,
link |
but also that no negative effects
link |
are showing up in the physiology
link |
as well as the psychology of these kids.
link |
So first I'll just tell you the basic outcome of the study,
link |
which was, here I'm paraphrasing,
link |
given twice daily, carnitine appeared to be effective
link |
in well-tolerated treatment
link |
for a group of children with ADHD.
link |
They showed significant abnormal behavior
link |
compared to these other boys.
link |
And now I'm moving to the table of results.
link |
They showed significant reductions
link |
in their so-called total problem score.
link |
The total problem score is a well-established measure
link |
of behavioral problems in kids with ADHD.
link |
And I should say adults with ADHD
link |
has to do with challenges in social and learning environments
link |
and how well or poorly an individual tends to perform.
link |
Reductions in attentional problems overall,
link |
reductions in delinquency,
link |
and most important for sake of today's discussion,
link |
significant reductions in aggressive behavior.
link |
Now, what's especially nice about this study, I think,
link |
is that even though it's a relatively small number
link |
of subjects and certainly it needs to be repeated
link |
in other studies and other laboratories,
link |
that they were able to confirm the shifts
link |
in L-carnitine within the bloodstream of these kids.
link |
That is, they were able to correlate the physiology
link |
with the psychological changes.
link |
In studies like this, and frankly, in all studies
link |
of human pharmacology, you have to worry about effects
link |
that show up, not just because of placebo effects,
link |
but because of so-called off-target effects
link |
or related things totally independent of the drug
link |
or the particular supplement
link |
that you happen to be looking at.
link |
To put it in the words of a great neuroscientist,
link |
unfortunately, he passed away some years ago,
link |
but he was a member of the National Academy,
link |
extremely accomplished neuroscientist,
link |
who once turned to me and said,
link |
never forget, a drug is a substance
link |
that when injected into an animal or a human being
link |
Meaning you can see effects of pretty much any drug
link |
or any supplement in most all conditions.
link |
However, it is in cases such as this study
link |
where you can quite convincingly see
link |
that the particular feature of physiology
link |
that you expected to change actually changed,
link |
and you see a psychological outcome
link |
that you can gain much greater confidence
link |
that the changes in delinquency,
link |
in this case, reduced delinquency,
link |
improved attention, reduced aggressiveness, and so forth,
link |
was at least somehow related to the shift
link |
in blood physiology and levels of L-carnitine
link |
or acetyl-L-carnitine and carnitine
link |
in the bloodstream of these children,
link |
as opposed to something else,
link |
like L-carnitine going and affecting some downstream target
link |
that you have no knowledge of.
link |
Now, of course, that's still entirely possible,
link |
but I think studies such as these increase our confidence
link |
that things like L-carnitine can be used
link |
perhaps in concert with things
link |
like omega-3 supplementation,
link |
diets that are biased towards increasing more tryptophan
link |
and therefore more serotonin,
link |
obviously avoiding things like alcohol,
link |
and as it appears from the study I just described,
link |
reducing one's intake
link |
or not consuming any caffeinated alcoholic beverages.
link |
Seems like it would be a good idea
link |
if your goal is to reduce aggressiveness
link |
to think about the hormone context
link |
and whether or not you tend to have higher testosterone
link |
and estrogen or lower testosterone and estrogen.
link |
Maybe even thinking about the work environment,
link |
whether or not you are existing
link |
in a particularly competitive work environment
link |
and even day life, time of year,
link |
and whether or not you're getting sufficient sunlight,
link |
whether or not you're avoiding light
link |
in the evening and so on.
link |
So studies such as this I think are useful
link |
because they point to the fact that very seldom, if ever,
link |
will there be one supplement or one nutritional change
link |
or even one behavioral change
link |
that's going to completely shift an individual
link |
from being aggressive and impulsive,
link |
but rather that by combining different behavioral regimens,
link |
by paying attention to things like time of year
link |
and work conditions and school conditions
link |
and overall levels of stress
link |
and likely therefore levels of cortisol, et cetera,
link |
that you can use behaviors, diet, and supplementation
link |
as a way to shift that overall internal milieu
link |
from one of providing a lot of internal hydraulic pressure,
link |
as it's been called throughout the episode,
link |
toward aggressive impulsivity
link |
and relax some of that hydraulic pressure
link |
and reduce aggressive tendencies.
link |
So once again, and frankly, as always,
link |
we've done a deep dive into the neurobiology
link |
and the psychology of what I believe
link |
to be an important feature of our lives,
link |
in this case, aggression.
link |
I want to point out that in a episode
link |
in the not too distant future,
link |
I'm going to be hosting Dr. Professor David Anderson
link |
from Caltech University,
link |
who is the world expert on the neurobiology of aggression.
link |
In fact, he is the senior author
link |
on many of the studies related
link |
to the ventromedial hypothalamus that I discussed today.
link |
Our discussion will touch on aggression, of course.
link |
So hearing today's episode
link |
will help you digest that information,
link |
but we are also going to talk about other emotional states.
link |
He is an expert, not just in aggression,
link |
but in motivated states related to sex
link |
and mating behavior, social relationships of all kinds,
link |
and how those relate not just to biology and psychology,
link |
but also certain forms of pathology,
link |
things like PTSD and the relationship, for instance,
link |
between anger, fear, anxiety, and depression,
link |
and many other important topics that I know many of you,
link |
if not all of you, will be interested in.
link |
In the meantime, I want to point you
link |
to his recently released and wonderful book entitled
link |
The Nature of the Beast, How Emotions Guide Us.
link |
And again, the author is David Anderson from Caltech.
link |
This is a wonderful book.
link |
It serves as a tremendous introduction
link |
to the history of the study of these areas,
link |
the current science and discoveries being made
link |
in these areas, all made accessible
link |
to the scientist and non-scientist alike.
link |
It's a very engaging read.
link |
And so much so that even though he was gracious
link |
in sending me a copy, I also purchased myself a copy
link |
to give to somebody who is a therapist,
link |
and I've purchased another copy to give to a high school kid
link |
that I mentor because he's very interested
link |
in the neuroscience of emotions.
link |
And I think we are all interested in emotions,
link |
not just fear and some of these negative states,
link |
not just aggression,
link |
but also the positive emotions of our lives.
link |
And so The Nature of the Beast, How Emotions Guide Us
link |
by David Anderson is a wonderful read.
link |
I can't recommend it highly enough.
link |
If you're learning from and or enjoying this podcast,
link |
please subscribe to our YouTube channel.
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That's a terrific zero cost way to support us.
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In addition, please subscribe to our podcast
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Please also check out the sponsors mentioned
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That is the best way to support this podcast.
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We also have a Patreon, it's patreon.com
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slash Andrew Huberman, and there you can support
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During today's episode and on many previous episodes
link |
of the Huberman Lab Podcast, we discussed supplements.
link |
While supplements aren't necessary for everybody,
link |
many people derive tremendous benefit from them
link |
for things like improving the transition time
link |
and the quality of your sleep
link |
and improving alertness and focus and so on.
link |
Anytime you're considering taking supplements,
link |
there are several key considerations.
link |
First of all, those supplements
link |
should be of the very highest quality.
link |
And you want to make sure that what's listed on the bottle
link |
is actually what's in the bottle,
link |
which is a problem for many supplement companies out there.
link |
The Huberman Lab Podcast is pleased to announce
link |
that we are now partnered with Momentous Supplements
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because we believe Momentous Supplements
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to be of the very highest quality
link |
of any supplements out there.
link |
And we've been working very closely with them
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in order to direct them to create supplements
link |
that are individual ingredient supplements
link |
of the particular quality and sources
link |
that we would like to see
link |
and that relate to the science and studies covered
link |
on the Huberman Lab Podcast.
link |
If you'd like to see some of those supplements,
link |
you can go to livemomentous.com slash Huberman,
link |
and there you will see some of the supplements
link |
that we've talked about on this podcast before,
link |
such as magnesium threonate for augmenting sleep,
link |
things like L-tyrosine for augmenting dopamine,
link |
and things like L-carnitine,
link |
which we've discussed on today's podcast.
link |
Right now, the list of supplements
link |
and the products that are there is only partial
link |
to what will soon be included in the future,
link |
so that's an ever-expanding catalog of, again,
link |
what we believe to be the very highest quality supplements
link |
For those of you that are interested in behavioral,
link |
nutritional, and supplementation-based tools
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for neuroscience and other aspects of your biology
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that impact your health and performance,
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we have a newsletter.
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It is a zero-cost newsletter.
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It's called the Neural Network Newsletter.
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You can go to HubermanLab.com, and there in the menu,
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You can just put your email.
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Once again, thank you for joining me
link |
for our discussion about the biology, psychology,
link |
and actionable tools around aggression,
link |
and as always, thank you for your interest in science.
link |
And as always, thank you for your interest in science.