Dr. David Anderson

What happens when you stimulate them, we don't yet know because we don't have a way to specifically do that without activating the male aggression neurons.

But I think they must be there for a reason because VMH is not traditionally the brain region to which male sexual behavior has been assigned.

That's another area called the medial preoptic area.

and there we have shown that there are neurons that definitely stimulate mating behavior in fact if we activate those mating neurons in a male while it's in the middle of attacking another male it will stop fighting start singing to that male and start to try to mount that male

until we shut those neurons off.

So those are the make love not war neurons, and VMH are the make war not love neurons.

And there are dense interconnections between these two nuclei, which are very close to each other in the brain.

But it's also possible that there are some cooperative interactions between those structures, as well as antagonistic interactions

And the balance of whether it's the cooperative or antagonistic interactions that are firing at any given moment in a mating encounter, as you suggest, may determine whether a moment of coital bliss among two lions may suddenly turn into a snap or a growl and a bearing of fangs.

We don't know that, but certainly the substrate, the wiring is there for that to happen.

When we made that discovery initially, it raised the question in my mind whether some people that are serial rapists, for example, and engage in sexual violence might in some level have their wires crossed.

in some way that these states that are supposed to be pretty much separated and mutually antagonistic are not and are actually more rewarding and reinforcing.

So I think of PAG like a old fashioned telephone switchboard.

There are calls coming in and then the cables have to be punched into the right hole to get the information to be routed to the right recipient on the other end of it.

Because pretty much every type of innate behavior you can think of

has had the PAG implicated.

In cross-section, the PAG kind of looks like the water in a toilet when you're standing over an open toilet bowl.

And if you imagine a clock face projected onto that, it's like the PAG has sectors

from one to 12, maybe even more of them.

And in each of those sectors, you find different neurons from the hypothalamus are projecting.