Tactile Perception of Spatially Distributed Vibratory Stimuli on the Fingerpad

Using a pin-array type tactile display as a stimulator of the finger pad, a psychophysical study was conducted on the vibrotactile perception. The passive touch with vibratory stimuli in the low frequency could be an alternative of the active touch for the presented stimuli: polygons, round shapes and gratings. As for the effect of frequency on the texture discrimination, the high correct answer proportions corresponded to the most sensitive frequency ranges of each mechanoreceptor. The spatial acuity decreased as the frequency of the stimuli increased when the stimuli presented by the equal number of contactors. As an analogy between color vision and tactile perception, a spatial configuration of the multiple contactors was proposed to deliver the intermediate pitch using the compound waveform defined as a sinusoidal stimulus which was presented by four contactors vibrating with 30Hz and 240Hz. The subjects felt qualitatively different the compound waveform and the pure-tone. When the high frequency component had 3 times the intensity of the other component, the perceived frequency of the compound waveform was about 120Hz which was much lower than the component frequency 240Hz. The experimental results were explained by the hypothesis of a ratio code, neural mechanism signaling the frequency of vibratory stimuli based on the ratio of the one-to-one activated population of mechanoreceptors. In addition, the intensity of the components also affected the overall perceived frequency. Thesis Supervisor: Dr. Mandayam A. Srinivasan Title: Senior Research Scientist, Department of Mechanical Engineering