Fine surface‐texture discrimination ability depends on the number of mechanoreceptors participating in the discrimination task

The purpose of this study was to investigate the relation between fine surface‐texture discrimination ability in tactile sensation and the number of mechanoreceptors participating in the discrimination task. Two experiments were performed. In experiment 1 the spatial‐summation effect was measured at the fingertips using aluminum oxide abrasive papers as stimuli, with grit values between 600 and 8000. Difference thresholds could not be determined when the area of the papers was 25 mm2. Thresholds were between 11.3 and 13.5 μm at 100 mm2, and they were between 3.14 and 5.58 μm at 400 mm2. In experiment 2 the difference thresholds of the texture‐discrimination tasks were measured at the fingertips and the thenar eminence using large‐sized (2500 mm2) abrasive papers with grit values between 400 and 8000. The difference thresholds were smaller at the thenar eminence than at the fingertips because the stimulated area at the thenar eminence was eight times larger than the area at the fingertips. From the results of experiments 1 and 2, it was concluded that the larger the number of mechanoreceptors which participate in the discrimination tasks, the smaller the difference thresholds. [Work supported by the Ministry of Education, Science and Culture, No. 07610093 and Mikiya Science and Technology Foundation.]