As it turns out, a bizarre new study involving rats is very informative about our own psyche.
Tickling is an extremely bizarre phenomenon, in which a light touch can send us either shrieking with laughter or screaming for mercy. Unlocking the secret behind tickling would help us understand a lot better how our brains and bodies work. Now, a new study takes a closer look at the subject by tickling rats.
The study, published in the journal Science and conducted by researchers at Humboldt University in Berlin, involved tickling and playing with rats in different circumstances. They found out something interesting: tickling happy rats activated a certain brain region, but this brain region in anxious rats didn’t respond to the same stimuli, according to the study.
Also, when scientists stimulated the brain area, the happy rats started to make high-pitched giggles, much like humans do, although theirs are much higher pitched.
“Rats emit ultrasonic vocalizations in response to tickling by humans,” the paper’s abstract states. “Tickling is rewarding through dopaminergic mechanisms, but the function and neural correlates of ticklishness are unknown. We confirmed that tickling of rats evoked vocalizations, approach, and unsolicited jumps (Freudensprünge). Recordings in the trunk region of the rat somatosensory cortex showed intense tickling-evoked activity in most neurons, whereas a minority of cells were suppressed by tickling. Tickling responses predicted nontactile neural responses to play behaviors, which suggests a neuronal link between tickling and play. Anxiogenic conditions suppressed tickling-evoked vocalizations and trunk cortex activity. Deep-layer trunk cortex neurons discharged during vocalizations, and deep-layer microstimulation evoked vocalizations. Our findings provide evidence for deep-layer trunk cortex activity as a neural correlate of ticklishness.”