Investigating the Tactile Thermal Grill Illusion
for Assessing Sensory Loss

Abstract

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This study investigates the perception of touch stimuli felt through a display that presents paradoxical thermal stimuli (Thermal Grill Stimuli), through combinations of warm and cool bars, eliciting an effect known as the Thermal Grill Illusion, which yields a warm-cool, pseudo-burning sensation, without any noxious or injurious effects.

The thermal grill stimuli consists of spatially alternating cool and warm bars. Touching only the warm bars or the cool bars alone does not induce discomfort, as the hot bars are not uncomfortably warm (at or below 40° C) and the cool bars are not uncomfortably cool (above 13° C). The electrothermal display used in our device is constructed from consumer electronic components, and the electrical voltages used are low. We have reviewed the safety and operation of the display and stimuli with a physician collaborator.

This experiment investigates whether the thermal grill illusion can be used in order to facilitate fast and robust assessment of sensory deficits. The Thermal Grill stimulus is known to evoke large and relatively unambiguous behavioral responses from what are otherwise comfortable temperatures. That is, subjects report an unambiguous sensation, even though the felt thermal signals are not too hot or too cool. The aim of this study is to quantify the magnitude of the Thermal Grill effect as a function of stimulus parameters and body site.

• S. Patwardhan, A. Kawazoe, D. Kerr, M. Nakatani, and Y. Visell. Dynamics and Perception in the Thermal Grill Illusion. in IEEE Transactions on Haptics. 2019.

• S. Patwardhan, A. Kawazoe, D. Kerr, M. Nakatani and Y. Visell, "Too hot, too fast! Using the thermal grill illusion to explore dynamic thermal perception,"  IEEE Haptics Symposium (HAPTICS), 2018,
  🏅 Honorable mention, finalists for Best student presentation award