[Equal-sensation contours and a threshold curve for low-frequency vibrotactile stimuli on the glabrous skin of the human hand].

Using vibrotactile stimuli, equal-sensation contours and a threshold curve were determined on the glabrous skin of the human hand. Equal-sensation contours were measured between 1 Hz and 16 Hz. When plotted on log-log coordinates, they monotonically decreased as a function of frequency and were downward by concaved. The threshold curve was measured between 1 Hz and 50 Hz. Its values decreased linearly from 1 Hz to 16 Hz, became constant at 16-35 Hz, and decreased again at 35-50 Hz. Therefore, at the stimulus range of 1-16 Hz, equal-sensation contours were downward concave and the threshold curve was more or less linear. This discrepancy seems to be caused by the differences in mechanoreceptor types which take part in subjective responses: suprathreshold sensation depends on several types of mechanoreceptors, whereas vibrotactile thresholds depends mainly on RA receptors (Meissner corpuscles).