When we run our fingers across a finely textured surface, small, complex vibrations are elicited in the skin, and specialized receptors embedded in the skin allow us to sense these vibrations. Different surfaces elicit different vibrations, and it is on the basis of these differences that we are able to discriminate silk from, say, satin. The ability to extract meaningful information from skin vibrations implies neural mechanisms that have yet to be discovered. This project investigates the mechanisms by which information about surface texture is extracted from texture-elicited vibrations. To this end, the Principal Investigator records (using a laser Doppler vibrometer) the skin vibrations elicited by everyday textured surfaces and examines the information conveyed. He then records the responses evoked by various textured surfaces in the nerve of Rhesus macaques and has human participants perform discrimination experiments using these same textures. Exploiting the well-documented homology between human and Rhesus sensory systems, he uses a variety of computational and machine learning techniques to reveal which aspects of the neural response account for our ability to distinguish between textures. Ultimately, the processing of skin oscillations constitutes a distinct and poorly understood mode of somatosensory processing. Indeed, while analogies have been drawn between visual and tactile processing of shape and motion, this second processing mode draws strong analogies with the auditory system. In both systems, stimulus information is extracted from spectrally complex oscillations (of the ear drum or the skin for audition and touch, respectively). In addition to their important scientific implications, results from this project will inform the development of sensorized upper-limb neuroprostheses and of virtual haptics displays. Finally, the project comprises an important educational and outreach component, with a strong emphasis on undergraduate education, recruitment of under-represented groups, and outreach to the general public.
