The Central Mechanism Underlying Extrapolation of Thermal Sensation

Extrapolation of thermal sensation (ETS) is a temperaturetuning phenomenon. Heat is felt outside the cold stimulator if given a single warm stimulus for 5 s and then both warm and cold stimulus for 0.5 s, while no such tuning is in reversed condition. The mechanism underlying ETS has not been clarified. We claim a common mechanism based on the transition of the spatiotemporal conditions among ETS, paradoxical heat sensation (PHS), and thermal grill illusion (TGI). We tested whether the addition and unmasking theory in TGI also works in ETS. Percentage hot judgment was found to increase as the temperature difference of stimuli increases, suggesting that hot sensation at extrapolation site can be the result of an addition of non-noxious warm and cold signals. On the other hand, the cold threshold was found to decrease as the distance between warm and cold stimulus increases, suggesting that the unmasking process occurs at the cold site. Our findings suggested that unmasking and addition process involve in the temperature-tuning phenomenon (ETS, TGI, and PHS) at the site with and without physical stimulation, respectively. The co-work of two processes forms a gate control model of temperature.