Amygdala's Acidic Aspiration Answer
A study in the journal Cell shows that the buildup of carbon dioxide when we stop breathing causes a pH change that signals proteins in the brain to force us to inhale. Karen Hopkin reports.

Maybe it’s happened to you. You think you have a fever. So you pop a thermometer in your mouth and try to breathe through your nose to get an accurate reading. But you’re totally stuffed up, so you experience this moment of complete panic because you can’t get enough air. Well, a new study in the journal Cell says you can thank your amygdala for that. Because this key member of the brain’s fear circuitry can directly sense suffocation, and trigger feelings of terror.

The amygdala plays a role in responding to threats, and it can kick off a fight-or-flight reaction when it senses danger. Now, this brain region is packed with a type of protein that’s activated by acid, and seems to be involved in an animal’s response to fear. Well, suffocation is pretty scary and signals to the brain that something isn’t right. And it does so by activating this acid-sensing protein.

When an animal can’t breathe, carbon dioxide builds up, and boosts the amount of acid in the body. The acid, in turn, turns on this protein, which then hits the panic button and tells the animal to do something. Even if, during the Thanksgiving meal, it’s just to remind the animal to stop swallowing and take a deep breath.

—Karen Hopkin