Displaying centre of pressure location by electrotactile stimulation using phantom sensation

Amputees not only lack motor function, but also sensory feedback of the missing limb. It has been shown that lower limb amputees can improve certain gait characteristics when they perceive additional information about the kinematics and kinetics of their prosthetic leg. In this paper, we address the question whether it is feasible to provide centre of pressure location information via electrotactile displays by exploiting the phantom sensation phenomenon, where relative intensity of two electrode pairs is used to encode position between them, creating a single illusory stimulus. Four healthy subjects were asked to identify different locations or movement patterns of the illusory stimulus on a discrete scale under static and dynamic conditions. These stimuli resembled CoP patterns in different locomotor activities. An average recognition accuracy of 73% (std. dev. 17%) was achieved under static conditions, and of 71% (std. dev. 11%) under dynamic conditions. This indicates that the proposed display and mapping can be used to present centre of pressure location, and future work will focus on evaluation with patients