2009 年 75 巻 754 号 p. 1698-1704
In order to enhance capability of the man-machine interface, we are attempting to investigate the influence of the proprioception on the cutaneous sensation. We performed a series of experiments based on psychophysics, in which we adopted a circle and eight kinds of oval as stimuli. The diameter of circle is 10mm, minor axes of eight kinds of oval are decreased in 3% step from circle, and each major axis is adjusted to make area of each oval be equal to the circle area. Human subjects judged which stimulus presented on right or left panel equals the circle. The experiment is conducted on both of fingertip and thenar parts to compare experimental sensitivity ratio of the thenar to the fingertip with estimated sensitivity ratio based on density of mechanoreceptor. The figure discrimination sensitivity of the thenar was inferior to that of the fingertip according to low density of mechanoreceptor in the thenar. Two-dimensional shape was not recognized by FA II (fast adaptive type II unit) but SA I (slowly adaptive type I unit) because the discrimination precision was not affected by cooling of specimen. Discrimination sensitivity was not different between free and restricted haptic motions. It is implied that the figure discrimination is modified by not only signals from mechanoreceptive units but also motor signal for the haptic motion.