A tickle can send a rat into a fit of ultrasonic giggles. New research reveals what goes on in a rat’s brain during a tickle attack.

Scientists knew rats loved to be tickled, especially on their backs and bellies. A tickled rat lets out tiny giggles, too high for us to hear. Special microphones captured the squeaks so they could be replayed in a lower register.

Belly and back tickles elicited giggles galore. Tail tickles, not so much.

The rats will chase a researcher’s hand for more. And even frolic about, in a newly described behavior called Freudensprünge, or “joy jumps”—

—but only if the rats are in the mood to be tickled. A bright light and platform make a rat anxious. And it won’t giggle when tickled.

Now, researchers linked these reactions to a specific brain region in the somatosensory cortex. Tickles activate these neurons. And stimulating those neurons makes the rats giggle even when they aren’t being tickled.

Whether a rat can tickle itself is a question for future research.