Discrimination Of Phantom Finger Sensation Through Transcutaneous Electrical Nerve Stimulation

The myoelectrical prosthestic hand on the market can help upper-limb amputees restoring part of motor function and improving the manipulation level of objects for prosthetic hand wearers.Although the current artificial prosthesis has reached a higher level in manipulation,the loss of sensory feedback still makes the movements have to rely on visual feedback,which not only affects the control accuracy,but also seriously decreases the amputees acceptance rate and utilization of prostheses.Transcutaneous electrical nerve stimulation of the phantom finger territories can provide a non-invasive sensory feedback for prostheses.Modulating the perceived intensity and perceived location through changing the stimulation parameters and electrodes are important biomimetic approaches to bionic touch for amputees.However,the encoding of perceived intensity and perceived position are limited to the discrimination ability of the subjects,whose quality of quantitative evalutaion are need to be measured.We use the classic psychophysics experiments,which based on the method of constant stimuli and 2AFC task paradigm,to measure those factors of detection thresholds,difference thresholds,perceived intensity and the discrimination ability of phantom finger territory in the means of modulating the parameters of pulse amplitude(PA),pulse frequency(PF)and pulse width(PW)?The results show that the subjects can experience a wide range of perceived intensity under three modulation.The detection thresholds among four phantom finger territories are 0.78 ~ 1.26 mA in PA,2.17 ~ 3.13 Hz in PF and 98.3 ~ 131 ?s.What's more,they can discern a small increment of stimulus intensity with Weber fraction spread in about 0.1 ~ 0.2.Participants in the multi-channel stimulation of the perceived location also have a high accuracy,which are 85.83%,67.67%,46.44% in one,two,four channels stimulation.The results of this experiment provide guidance for coding with perceived intensity and perceptual position with external stimuli for restoring sensory feedback on prostheses by TENS of PFTs.