Do rats make ultrasonic sounds when people tickle them?

Details

Researchers tickled rats and recorded activity in the part of the brain’s outer layer that processes touch from the trunk. Tickling elicited calls, approach and spontaneous jumps. Most recorded nerve cells became strongly active during tickling, but a minority became less active.

The cells’ responses to tickling also predicted their responses during play behaviors without touch, suggesting a neural link between tickling and play. Cells in deeper layers of the recorded region were active during calls, and electrical stimulation of those layers also elicited calls.

These findings link activity in the deeper layers to ticklishness; they do not establish that this region alone creates the experience. Anxiety-inducing conditions reduced both the calls and activity in the trunk-related region, so the response depended on the conditions. The abstract does not report the number of rats or the sizes of these effects.