Response characteristics of cutaneous mechanoreceptors to vibratory stimuli in human glabrous skin.

We investigated the responsiveness of mechanoreceptors in the glabrous skin of the hand to triangular vibratory stimuli when the frequency and applied pressure to the skin were varied. Using a microneurographic technique, 13 single afferent activities were recorded from 4 kinds of mechanoreceptors. Both fast-adapting (FA) and slow-adapting (SA) units were sensitive to the vibratory stimuli. The relationship between the most sensitive frequency and applied pressure to the skin were analyzed as a tuning curve. FA-type I (FAI) was sensitive to vibratory stimuli at 30-40 Hz and the frequency which entrained one-to-one discharge at lower pressure was between 10 and 80 Hz. FA-type II (FAII) sensitivity was augmented sharply over 60-100 Hz. SA-type I (SAI) and SA-type II (SAII) responsiveness was almost the same and characteristic sensitivity to the vibratory stimuli was revealed under 15 Hz. Functional roles of these units, especially type I units, are discussed in relation to active touch such as texture discrimination with a finger.