Episode 89: Dr. David Anderson – The Biology Of Aggression, Mating, & Arousal | Huberman Lab

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Key Takeaways

  • The areas of the brain that control feeding, fleeing, fighting, and mating are in close proximity in the brain possibly to help the animal decide what behavior to prioritize and what to shut down at any given moment
  • “Aggression refers more to a description of behavior than the internal state. Aggression could reflect fear, anger, hungry (in animals).” – Dr. David Anderson
  • Estrogen and the aromatase of testosterone into estrogen is really what generates aggression, not testosterone alone
  • Arousal is tethered to the mating and reproductive process: without a seesaw between sympathetic and parasympathetic, there is no mating
  • The same behavior can reflect different states and different states can converge on multiple behaviors
  • In social animals and humans, the body secretes higher levels of tachykinin when we are not socially connected enough – symptoms: increased irritability, paranoia, fear, loneliness
  • Emotion involves bidirectional communication between the brain and body, mediated by the peripheral nervous system, autonomic nervous system, and Vagus nerve

Introduction

David Anderson, Ph.D., (lab website) is a world expert in the science of sexual behavior, violent aggression, fear, and other motivated states. Dr. Anderson is a Professor of Biology at the California Institute of Technology (Caltech), a member of the National Academy of Sciences, and an investigator with the Howard Hughes Medical Institute (HHMI). His research focuses on understanding the neurobiology of emotion.

In this episode, Andrew Huberman & David Anderson discuss how states of mind and body arise, persist, drive our behavior, and influence the way we interpret our experience and surroundings. They also delve into the kinds of arousal, types of violent aggression, mental health, mental illness, and much more!

Host: Andrew Huberman (@hubermanlab)

Book: The Nature of the Beast: How Emotions Guide Us by David J. Anderson

Emotions Versus States

  • Emotions, arousal, and sleep are types of internal states – meaning they change the input/output transformation of the brain
  • Emotion is a neurobiological process instead of a psychological process, not just a “feeling”
  • “[Emotion] is the part of the iceberg that’s below the surface, the feeling is the tip.” – Dr. David Anderson
  • Dimensions of states: arousal, intensity, valence (good or bad)
  • Emotion states and motivation states are very persistent – though not all states have persistence (think of hunger which passes when you eat)
  • Motivation states are specific: find and eat food, find and drink water, etc.
  • Valence is less about which specific neurotransmitters are involved and more about which circuits are involved

Aggression

  • “Aggression refers more to a description of behavior than the internal state. Aggression could reflect fear, anger, hungry (in animals).” – Dr. David Anderson
  • Studies have triggered aggression by stimulating the ventral medial hypothalamus (VMH) in mice – the mice like the activation and use the aggression offensively, they leverage it on mice they want to attack or mate (or both)
    • If there’s nothing for the mouse to attack, it’ll just roam around the cage – the minute another mouse is there the story changes
  • VMH projects to and gets input from about 30 different brain regions – it’s taking in information and synthesizes it to weigh whether to engage in path or backoff
  • Circuitry complexity: there’s close positioning of neurons that generate fear is next to the neurons that generate offensive aggression
  • Fear neurons sit on top of aggression neurons; when activated they elicit arousal
  • Defensive behaviors and fear may have arisen before offensive aggression (you can only think about who’s going to be the alpha male when your needs are met)
  • Fear in defensive and offensive aggression: intense fear shuts down offensive aggression versus defensive aggression which is enhanced by fear
  • Accumulated pressure can come from something you’re deprived of and need, or something you want to do driving pressure
  • Sex differences in aggression: female mice only fight when they’re nurturing and nursing pups (virgin mice will not fight when VMH is stimulated, not fight); male-specific neurons in VMH are sex-specific

The Role Of Testosterone & Estrogen In Aggression, Mating

  • An increase in testosterone does not make humans or animals aggressive – it really makes them more of the way they naturally are (i.e., if you’re naturally a jerk you’ll be more of a jerk)
  • Testosterone plays a role in generating aggression – but, the specific hormones that generate aggression through VMH is actually the estrogen
  • A castrated mouse will fight again if given estrogen, bypassing the need for testosterone completely
  • Many of the effects of testosterone are mediated by its conversion to estrogen (aromatization)

Mating

  • Information that there’s an object in front of you comes together with the drive state and tells the animal to pull the trigger and go
  • There’s a group of males on social media that are part of a “no masturbation” group, encouraging it as a way to maintain their motivation to go out and seek mates and avoid porn addiction, etc.
  • Fetishes are a fixation or almost requirement of things that have a disgusting connotation (feces, dead bodies, feet) to become sexually aroused
  • If reward states are turning on in association with something (even if it’s gross to other people), you can be conditioned and change the valence
  • In mice, different neurons are activated during sniffing, mounting, thrusting, and ejaculation
  • There could be something that ties thermoregulation to aggressiveness and mating behavior
  • Mounting behavior can be about sexual expression or about asserting dominance – in mice, for example, males sing when they mount a female but not at all when they mount a male so you can distinguish its intention  
  • Female-female mounting in mice: it takes place, but the function, hierarchy goal or reason is unknown

Periaqueductal Gray (PAG), Tachykinin & Pain

  • The PAG has at least a dozen sectors of neurons projecting from the hypothalamus PAG is responsible for some endogenous pain control – it doesn’t hurt as bad to get punched while you’re in a fight as it will after
  • PAG is involved in fear, panic behavior, running away, freezing, etc.
  • Fear-induced analgesia: when an animal is in a high state of fear, pain responses are suppressed
  • Tachykinin is a short protein encoded by genes in specific neurons which are released together with classic neurotransmitters
  • The body secretes higher levels of tachykinin when we are not socially connected enough
  • Tachykinin symptoms: increased irritability, paranoia, fear, loneliness
  • Social isolation increases aggressiveness and the level of tachykinin in the brain
  • If you socially isolate a mouse, you cannot put it back in the cage with its family because it will kill them! Think about the implications of solitary confinement
  • Some new drugs target this specific protein, but pharmaceutical companies are reluctant for some reason

Human Studies Of Emotion

  • People associate certain parts of their body with certain emotions or feelings – our subjective feeling of emotion is in part associated with a sensation of something happening in a specific part of our body
  • Emotion involves bidirectional communication between the brain and body, mediated by the peripheral nervous system, autonomic nervous system, and Vagus nerve

Resources

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Notes By Maryann

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