An engineered tactile afferent modulation platform to elicit compound sensory nerve action potentials in response to force magnitude

In the near future, upper limb prostheses may interface with peripheral nerves of amputees to help restore vital somatosensory feedback. Achieving that goal requires the transformation of forces artificially sensed in our environment into the depolarization of afferents, by delivering levels of charge adequate for signaling tactile sensory cues yet avoiding tissue damage. The objective of the work herein was to build and test a tactile afferent modulation platform engineered to transform force data input, from an artificial sensor under ramp-and-hold stimuli, into the output of discrete charge-balanced pulses to the rat's acute sural nerve thereby eliciting compound sensory neural action potentials (CSNAPs). In vivo experiments, to stimulate both tactile end organs mechanically and sural nerves electrically, helped fit the model's empirical parameters. Input-output relationships were validated by comparing CSNAPs elicited by the tactile afferent modulation platform with those of natural end organs. The results replicated the natural response where increased force magnitude increased both CSNAP firing rates and waveform amplitudes. Next steps will involve the integration of the engineered platform with a regenerative peripheral nerve interface for the evaluation of its long-term reliability.