Touch on predefined areas on the forearm can be associated with specific fingers: Towards a new principle for sensory feedback in hand prostheses

Abstract

Objective: Currently available hand prostheses lack sensory feedback. A “phantom hand map”, a referred sensation, on the skin of the residual arm is a possible target to provide amputees with non-invasive somatotopically matched sensory feedback. How-ever, not all amputees experience a phantom hand map. The aim of this study was to explore whether touch on predefined areas on the forearm can be associated with specific fingers. Design: A longitudinal cohort study. Subjects: A total of 31 able-bodied individuals. Methods: A “tactile display” was developed consisting of 5 servo motors, which provided the user with mechanotactile stimulus. Predefined pressure points on the volar aspect of the forearm were stimulated during a 2-week structured training period. Results: Agreement between the stimulated areas and the subjects’ ability to discriminate the stimulation was high, with a distinct improvement up to the third training occasion, after which the kappa score stabilized for the rest of the period. Conclusion: It is possible to associate touch on intact skin on the forearm with specific fingers after a structured training period, and the effect persisted after 2 weeks. These results may be of importance for the development of non-invasive sensory feedback systems in hand prostheses.