Modulation Ranges of Different Sensations for Coding Electrically Evoked
Tactile Sensory Feedback
Abstract
The ability to perceive prosthetic grasping may enable amputees to
better interact with external objects. This may require customized
coding of multiple sensory feedback for each amputee. This study
developed a protocol to determine optimal modulation ranges of
sensations elicited by transcutaneous electrical nerve stimulation
(TENS). These sensations that were referred to the lost fingers provided
the possibility for restoring multi-modalities of sensory feedback for
amputees with evoked tactile sensation (ETS) non-invasively. To match
the restricted projected finger map area, smaller electrodes must be
used to deliver electrical stimulation for multi-channel sensory
information, which resulted in fewer types of sensations. Our protocol
provided comprehensive information for optimal selection of amplitude
and frequency in a personalized, pulse-width encoding paradigm. The good
sensitivity for vibration and buzz in both able-bodied and amputee
subjects suggested that perceptual intensity can be effectively
modulated to convey sensory information via either of the sensations.
The efficacy of this protocol in sensory coding for forearm amputees was
demonstrated in finger-specific identification experiment. This protocol
may allow customization of ETS-based sensory feedback with an optimal
encoding strategy for individual amputees.