How Fear Persists in the Mouse Brain

Most people have experienced, at some point in their lives, a sudden unexpected fright. Even after a shadowy figure in a darkened room turns out to just be a chair, your heart rate is still high, your palms stay sweaty, and your senses remain alert for another threat. This sort of lasting response is an example of a persistent internal state. The phenomenon of persistence is what distinguishes an internal emotional state from a reflex, such as jumping when hearing a loud noise.