Humans, but not animals, perceive the thermal grill illusion as painful.

Simultaneous presentation of alternating innocuous warm and cold stimuli induces in most humans a painful sensation called thermal grill illusion (TGI). Here, pain is elicited although nociceptors are not activated. Upon back-translation of behavioural correlates from humans to animals, we found that neither cats nor rodents show adverse reactions when exposed to TGI stimulation. These results question that a TGI observed as a pain-related change in behaviour can be elicited in animals. While distinct neuronal patterns as previously reported may be measurable in animals upon TGI stimulation, their translational meaning towards the sensation elicited in humans is unclear.