Dissociation of Vibrotactile Frequency Discrimination Performances for Supra-Threshold and Near-Threshold Vibrations

Abstract

For the wide range of vibration frequencies, the human capacity for vibrotactile frequency discrimination has been reported constant. However, vibrotactile detection depend on two different receptors, one is Meissner corpuscle for low frequencies and the other is Pacinian corpuscle for high frequencies. To examine the impact of input pathway on frequency discrimination task, discrimination capacity has been compared directly by using supra-threshold and near-threshold stimuli since near-threshold stimuli mainly activate one input pathway. Each standard frequencies 15, 30, 60, 120, 240 and 480 Hz at amplitude 6dB and 16 dB detection threshold, was paired with a series of comparison frequencies, and discrimination capacity was quantified by the discriminable frequency increment (Δf) and the Weber Fraction (Δf/f). The result revealed constant and good discrimination capacities for strong stimulus conditions but discrete and bad capacities for weak stimulus conditions. Near-threshold stimuli produced a marked impairment in vibrotactile discrimination at the high standard frequencies around 240 Hz, probably detected by Pacinian corpuscle, but relatively little effect at lower frequencies, mainly detected by Meissner corpuscle.