Modeling and Simulation of Thermal Grill Illusion Using Neurophysiological Theory

The Thermal Grill Illusion (TGI) is a temperature-based perceptual illusion in which innocuous warm and cold stimuli evoke pain when applied simultaneously in a juxtaposed pattern. Based on neurophysiological and psychological findings, several theories have been proposed to explain the mechanisms behind TGI. However, the significance of an analytical model for TGI is not addressed in the literature. This study focuses on developing an analytical model based on the “disinhibition theory” to predict the intensity of TGI pain. A psychophysical experiment on perceived TGI pain was first conducted, and then an analytical model was developed. The model’s objective is to predict the neuronal activity of pain-sensitive HPC (Heat-Pinch-Cold) nerve fibers by leveraging the existing popular models of warm and cold receptors. An experimental thermal grill setup was used to provide five temperature differences between warm and cold grills (each repeated three times). Participants rated the perceived TGI pain sensation on a Likert scale of one to ten. Both the experimental results and the simulation showed a monotonically increasing relationship between temperature differences and the perceived TGI intensity. The proposed model bridges the gap between neurophysiological and psychophysical knowledge of TGI, potentially aiding thermal display designs.