Discrimination of electrotactile stimulus location on and across fingertips.

摘要

Underneath the skin surface of human fingertips, high concentrations of mechanoceptors are used to transduce surface perturbations into a high resolution picture of events occurring along the fingertip. Electrotactile stimuli are transduced across the skin very differently than mechanical perturbations on the skin surface. On an individual fingertip this may lead to differences in one's ability to determine the location of an electrotactile versus a mechanical stimulus. Though the mechanism of transduction of electrotactile stimuli is fundamentally different from mechanical stimuli, ultimately interpretation of these signals depends on the same network of peripheral, spinal, and cortical neurons. Here the ability to discriminate electrotactile stimulus location was examined to determine the differences between discrimination of these signals on an individual fingertip and across several fingertips.;The results of these studies suggest that the locations of electrotactile stimuli are largely perceived similarly to mechanical perturbations. Additionally, hand posture's influence on the presence of the cutaneous rabbit effect across the fingertips suggests that the unimodal tactile map in area 3b is not likely to be the seat of this tactile illusion, postural information must be encoded into the interpretation of this illusory perception either upstream or downstream of this area.;The first two studies investigated the extent to which the location of electrotactile stimuli was discriminated similarly to mechanical stimuli. Despite the differences between the processing of these two input signals, electrotactile stimuli were discriminated similarly to very light weight mechanical perturbations on individual fingertips. Though the second study confirmed this result, it revealed that the differences in how these signals are transduced were responsible for producing different error distributions under electrotactile stimulation and mechanical perturbation. The final three studies examined the interpretation of discrete electrotactile stimuli delivered across the index, middle, ring, and little fingertips. Here the cutaneous rabbit effect, a tactile illusion, was induced across the fingertips in certain postures for the first time. Further, it was identified that posture had a significant effect on the perception of this illusion. Finally, a possible subpopulation was identified that was less susceptible to the illusion as produced by electrotactile stimuli across the fingertips.