We can eat for two reasons, seeking pleasure, like tasty food, or avoiding pain, like being hungry. How can we find a treatment for compulsive overeating without messing up the hunger driven feeding that we need to survive? The first step is to understand how the brain gives rise to feeding behavior.
This fully-fed mouse is just exploring a space completely devoid of any food. Here we're using optogenetics to target neurons living in the hypothalamus, sending messages down wires aimed at the midbrain. When I turn the light on right here, you can see that the mouse immediately begins licking the floor. This seemingly frenzy behaviour is about to escalate into something I find really incredible. It's kind of trippy, actually, ready? That's right here. He picks up his hands as if he is eating a piece of food, but there's nothing there. This circuit is sufficient to drive feeding behavior in the absence of hunger, even in the absence of food.
I can't know for sure how this mouse is feeling, but I speculate these neurons drive craving based on the behaviors we elicit when we target this pathway. Turn the light back off. Animals back to normal. When we silence this pathway, we can suppress, reduce compulsive overeating without altering hunger driven feeding.