Characterization of Sensory Perception Associated with Transcutaneous Electrostimulation Protocols for Tactile Feedback Restoration

One of the major difficulties faced by upper limb prosthesis users is the absence of tactile sensory feedback, which is fundamental to handling objects. Tactile feedback is required to estimate texture and shape of objects, enabling the subject to adjust the forces required to manipulate things and avoid slip. In the absence of tactile sensory feedback, the users become dependent of other kinds of feedback, such as visual or auditory, which are not effective every time. Aiming to overcome the limitations encountered by upper limb prosthesis users, we developed a protocol to characterize sensation caused by a modulated frequency transcutaneous electrostimulation. We realized that the frequency modulation can change the haptic intensity and that the amplitude of the stimulation directly influences the perception of the frequency change and the intensity of the perceived sensation. While the threshold of perception of discrete or continuous stimuli varied for each volunteer, the volunteer V1 did not have the perception of continuous sensation in the frequencies used, and V4 had this perception only with the amplitude of 1 mA. While for volunteers V2 and V4, this threshold was 50 and 100 Hz for the three experimental blocks, respectively. The volunteer V5 and V6 had different thresholds according to the stimulation current.