Touch Perception Threshold in Terms of Amplitude and Rate of Skin Deformation

Abstract

This chapter discusses the touch perception threshold in terms of amplitude and rate of skin deformation. The tactile threshold is measured on the fingertips of normal adults using half cycle sinusoidal mechanical pulses from a minishaker monitored by a Wave Tek stimulator. The pulse frequency is varied to produce various slow and rapid displacements in imitation of natural tactile stimuli that would be composed of different rates, and different amplitudes, of deformation. On the fingertips, the touch perception threshold is about 5 pm on stimulation with rapidly rising mechanical pulses. The low value indicates that the threshold sensation for touch is mediated by Pacinian corpuscles. With slow pulse stimulation, the threshold rose sharply when the displacement rate fell below 0.2 mm/sec. The threshold difference limen was a fraction of the absolute value of the threshold amplitude. The stimulation technique provides a quick and sensitive method for clinical testing of impaired sensibility.