RESUMEN
Introduction: Electrical stimulation is increasingly relevant in a variety of medical treatments. In this study, the quality of referred sensations evoked using surface electrical stimulation was evaluated using the rubber hand and foot illusions. Methods: The rubber hand and foot illusions were attempted under 4 conditions: (1) multi-location tapping; (2) one-location tapping; (3) electrical stimulation of sensation referred to the hand or foot; (4) asynchronous control. The strength of each illusion was quantified using a questionnaire and proprioceptive drift, where a stronger response suggested embodiment of the rubber limb. Results: 45 able-bodied individuals and two individuals with amputations participated in this study. Overall, the illusion evoked by nerve stimulation was not as strong as illusions evoked by physically tapping but stronger than the control illusion. Conclusion: This study has found that the rubber hand and foot illusion can be performed without touching the distal limb of the participant. Electrical stimulation that produced referred sensation in the distal extremity was realistic enough to partially incorporate the rubber limb into a person's body image.
RESUMEN
INTRODUCTION: Given the lack of haptic feedback inherent in prosthetic devices, a natural and adaptable feedback scheme must be implemented. While multimodal feedback has proven successful in aiding dexterous performance, it can be mentally tasking on the individual. Conversely, cross-modal schemes relying on sensory substitution have proven to be equally effective in aiding task performance without cognitively burdening the user to the same degree. OBJECTIVES: This experiment investigated the effectiveness of the cross-modal feedback scheme through using audio feedback to represent prosthetic grasping strength during dynamic control of a prosthetic hand. METHODS: A total of five individuals participated in two sets of experiments (four subjects in the first, one subject in the second). Participants were asked to control the grasping strength exerted by a prosthetic hand while using real-time audio feedback in order to reach up to three different levels of force within a trial set. RESULTS: The cross-modal feedback scheme successfully provided users with the robust ability to modulate grasping strength in real-time using only audio feedback. CONCLUSION: Audio feedback effectively conveys haptic information to the user of a prosthetic hand. Retention of the training knowledge is evident and can be generalized to perform new (i.e. untrained) tasks.