Human tactile detection thresholds: modification by inputs from specific tactile receptor classes

Publisher Website
Google Scholar
Abstract
Human detection thresholds for a vibratory stimulus applied to the volar surface of the index finger were examined under conditions where afferents from specific tactile receptor classes were simultaneously activated from the thenar eminence. Experiments were designed to test whether stimuli previously shown to induce afferent inhibition of tactile neurons in the cuneate nucleus of the cat could modify human subjective performance in a tactile detection task. Conditioning stimuli to the thenar eminence were usually of 3 forms; steady indentation to engage slowly adapting tactile receptors; 300 Hz vibration to engage Pacinian corpuscles; and 30 Hz vibration to engage the intradermal, rapidly adapting tactile receptors, thought to be Meissner''s corpuscles. In 10 subjects the mean detection threshold for a 30 Hz test stimulus in the absence of conditioning stimulation was 8.6 .+-. 1.0 .mu.m (SE). Detection thresholds were increased substantially in the presence of a 300 Hz, 100 .mu.m conditioning stimulus (mean increase 11.1 .+-. 2.0 .mu.m), whereas minor or insignificant effects were seen with conditioning stimuli consisting of 30 Hz, 100 .mu.m (mean increase 1.4 .+-. 0.8 .mu.m), steady indentation, 1.5 mm in amplitude (mean increase 1.3 .+-. 0.7 .mu.m), or 300 Hz, 100 .mu.m to the contralateral thenar eminence (mean increase 0.4 .+-. 0.5 .mu.m). The 300 Hz conditioning stimulus to the ipsilateral thenar eminence caused a marked increase in detection thresholds at all test stimulus frequencies over the range 10-450 Hz. The effects of the conditioning stimulation operated on inputs from Pacinian corpuscles, responsible for vibration detection at 80-450 Hz and on inputs from the intradermal, rapidly adapting receptors responsible for vibration detection at 10-80 Hz. The band width of conditioning vibratory frequencies, effective at amplitudes of 100 .mu.m in bringing about increases in detection threshold, extended from 50-80 Hz to 300 Hz, the maximum tested. While amplitudes of 1-2 .mu.m produced clear increases in detection thresholds with conditioning stimuli of 300 Hz, amplitudes of > 200 .mu.m were needed at 30 Hz. Elevations in detection threshold are consistent with an afferent-induced inhibitory action exerted at synaptic relays of the sensory pathway by tactile inputs arising exclusively or predominantly from Pacinian corpuscles.

This publication has 36 references indexed in Scilit: