Single-site non-invasive peripheral nerve stimulation with multidimensional encoding enables object differentiation using a myoelectric prosthetic hand

Background: This study aimed to evaluate whether a multidimensional
encoding approach, delivered through a single site of peripheral nerve
stimulation (PNS), could support object discrimination using a sensorized
myoelectric prosthetic hand. Methods: Ten participants without an
amputation received stimulation to the median nerve at the wrist, while
four participants with transradial amputations received stimulation to the
ulnar nerve near the elbow. Electrical stimulation was provided via
transcutaneous electrical neural stimulation (TENS) to either the wrist
(#_msocom_2) or the residual limb respectively. Force and aperture sensors
embedded in a multi-dexterous myoelectric prosthesis were used by the
participants to drive a multidimensional encoding approach. The
multidimensional encoding approach provided percepts of flutter frequency
and intensity in a single percept area. All participants were blindfolded
and wore noise-canceling headphones during the task, which involved
discriminating between six objects varying in size  (two levels)
and compliance (three levels). Results: All participants performed
significantly above chance in identifying the objects. Notably, all four
participants with amputations successfully used multidimensional percepts
felt in their phantom limbs to differentiate between the six objects.
Their performance was comparable to – or in some cases exceeded – that of
the participants without amputations. Conclusion: A multidimensional
encoding approach using TENS-based peripheral nerve stimulation can
effectively convey meaningful sensory information—such as object size and
compliance—to individuals using a sensorized myoelectric prosthesis. This
approach enables perception of complex sensations in the phantom limb and
may reduce the number of stimulation sites needed, offering a promising
direction for improving haptic feedback and reducing abandonment of
prostheses.