Object Discrimination Using Electrotactile Feedback

A variety of bioengineering systems are being developed to restore the sense of touch in individuals who have lost this mode of sensory feedback because of spinal cord injury, stroke, or amputation. Typically, these systems detect touch pressure on the fingers of an insensate hand (or from a prosthetic hand in the case of amputees) and deliver the detected pressure information to sensate skin above the site of injury (for example, on the back of the neck) by electrically stimulating that skin with an intensity that matches the detected pressure. We implemented a project that involves developing a method to artificially represent tactile and proprioceptive sensations using electrotactile feedback in prosthetic users. Our system uses one set of electrodes to provide information about contact forces applied by the digits and a separate set to indicate aperture of the hand. We tested the ability of five intact human subjects to distinguish objects of varying weight, width and compliance based on electrotactile feedback arising from sensors placed on the hand of an experimenter (not visible to the subject) grasping and lifting the test objects. Over the course of five separate training sessions, we observed a statistically significant (P=0.026) improvement in the mean performance of all subjects. Thus, this study serves as proof that human subjects can learn to make sense of multichannel-multivariable electrotactile feedback to comprehend certain physical features associated with an object