USING ELECTRICAL NOISE TO ENHANCE THE ABILITY OF HUMANS TO DETECT SUBTHRESHOLD MECHANICAL CUTANEOUS STIMULI

Stochastic resonance (SR) is a phenomenon wherein the response of a no nlinear system to a weak input signal is optimized by the presence of a particular, nonzero level of noise. Our objective was to demonstrate cross-modality SR in human sensory perception. Specifically, we were interested in testing the hypothesis that the ability of an individual to detect a subthreshold mechanical cutaneous stimulus can be signifi cantly enhanced by introducing a particular level of electrical noise. Psychophysical experiments were performed on 11 healthy subjects. The protocol consisted of the presentation of: (a) a subthreshold mechani cal stimulus plus electrical noise, or (b) no mechanical stimulus plus electrical noise. The intensity of the electrical noise was varied be tween trials. Each subject's ability to identify correctly the presenc e of the mechanical stimulus was determined as a function of the noise intensity. In 9 of the 11 subjects, the introduction of a particular level of electrical noise significantly enhanced the subject's ability to detect the subthreshold mechanical cutaneous stimulus. In 2 of the 11 subjects, the introduction of electrical noise did not significant ly change the subject's ability to detect the mechanical stimulus. The se findings indicate that input electrical noise can serve as a negati ve masker for subthreshold mechanical tactile stimuli, i.e., electrica l noise can increase the detectability of weak mechanical signals. Thu s, for SR-type effects to be observed in human sensory perception the noise and stimulus need not be of the same modality. From a bioenginee ring and clinical standpoint, this work suggests that an electrical no ise-based technique could be used to improve tactile sensation in huma ns when the mechanical stimulus is around or below threshold. (C) 1998 American Institute of Physics.