Dr. David Anderson

And the other one is predatory aggression.

where the cat has its ears forward and it's like batting with its paw at a mouse-like object like it wants to catch it and eat it.

If you think of ventromedial hypothalamus like a pear sitting on the ground, the fat part of the pear near the ground is where the aggression neurons are, but the upper part of the pear has fear neurons.

Fast forward from that, from a lot of work from Dayu now on her own at NYU and with her postdoc, Anna-Gret Faulkner, there's evidence that the type of fighting that we elicit when we stimulate VMH is offensive aggression that is actually rewarding VMH.

to male mice.

They like it.

Male mice will learn to poke their nose or press a bar to get the opportunity to beat up a subordinate male mouse.

It has a positive valence.

So it's become clear that if you want to call it the state of aggressiveness is multifaceted.

It depends on the type of aggression and it involves different sorts of circuits.

If you think...

From an evolutionary perspective, it might have been the case that defensive behaviors and fear arose before offensive aggression.

Because animals first and foremost have to defend themselves from predation.

by other animals.

And maybe it's only when they're comfortable with having warded off predation and made themselves safe that they can start to think about who's gonna be the alpha male in my group here.

And so it could be that if you think that brain regions and cell populations evolve by duplication and modification,

of pre-existing cell populations.

That might be the way that those regions wound up next to each other, but I think there must be a functional part as well.

So one thing we know about offensive aggression is that strong fear shuts it down.

Whereas defensive aggression, at least in rats, is actually enhanced by fear.