Thermal intensity perception under thermo-tactile interaction
Hsin-Ni Ho, Junji Watanabe, Hideyuki Ando, Makio Kashino
Poster
Time: 2009-06-29 11:00 AM – 12:30 PM
Last modified: 2009-06-04
Abstract
Thermal referral is first demonstrated with touching three stimulators with the middle three fingers of one hand. When the outer two stimulators were cold (warm) and the center stimulator was thermally neutral, cold (warmth) was felt at all three fingers. This illusion has been shown to result from the mislocalization of thermal sensations to the site of simultaneous tactile stimulation. Although the influence of the simultaneous tactile stimulation on the thermal localization has been studied extensively, its influence on the perceived thermal intensity has not yet been explored. Therefore, the present study investigated whether the simultaneous tactile stimulation also affects the perceived thermal intensity. We first investigated the perceived thermal intensity under no referral condition, in which two thermal stimulators were presented to two of the three fingers while the other finger held in the air. The stimulation levels of these two thermal stimulators, △Tsti, were ±5, 7 , and 10 degree C. The perceived thermal intensity at the two fingers under different stimulation levels was evaluated by comparing it to the perceived thermal intensity produced by the reference stimulation presented to the corresponding three fingers of the other hand. The level of the reference stimulation varied according to the adaptive staircase method to determine an equivalent stimulation level, △Teqv, at which the thermal intensity perceived at two hands were the same. The results indicated the relation between △Teqv and △Tsti to be: △Teqv = 0.79△Tsti for cooling and △Teqv = 0.80△Tsti for warming. The same procedure was adopted to investigate the perceived thermal intensity under thermal referral condition. The only difference was that the finger that was held in air in the previous experiment was now touched the neutral stimulator. The relation between △Teqv and △Tsti under thermal referral condition was found to be: △Teqv = 0.63△Tsti for cooling and △Teqv = 0.60△Tsti for warming. An one-way ANCOVA with experimental condition (no referral / thermal referral condition) as the fixed factor, △Tsti as the covariate and △Teqv as the dependent variable indicated that the perceived thermal intensities are significantly different between two experimental conditions for both cooling and warming stimulation. These results demonstrated the influence of the simultaneous tactile stimulation on the perceived thermal intensity and indicated the redistribution of thermal sensations under thermal referral.