Evoked Haptic Sensation in the Hand With Concurrent Non-Invasive Nerve Stimulation

Abstract

Objective: Haptic perception is critical for prosthetic users to control their prosthetic hand intuitively. In this study, we seek to evaluate the haptic perception evoked from concurrent stimulation trains through multiple channels using transcutaneous nerve stimulation. Methods: A 2x8 electrode grid was used to deliver current to the median and ulnar nerves in the upper arm. Different electrodes were first selected to activate the sensory axons, which can elicit sensations at different locations of the hand. Charge-balanced bipolar stimulation was then delivered to two sets of electrodes concurrently with a phase delay (dual stimulation) to determine whether the evoked sensation can be reconstructed from sensations of single stimulation delivered separately at different locations (single stimulation). The temporal delay between the two stimulation locations were altered to evaluate potential interference. The short-term stability of the haptic sensation was also evaluated. Results: The evoked sensation during dual stimulation was largely a direct summation of the sensation from single stimulations. The delay between the two stimulation locations had minimal effect on the evoked sensations which was also stable in the short-term. Conclusion: Our results indicated that the haptic sensations at different regions of the hand can be constructed by combining individual stimulation locations directly. The interference between stimulations were minimal.

Object stiffness recognition using haptic feedback delivered through transcutaneous proximal nerve stimulation

“…The matrix linked one of the 16 electrodes among the 2 × 8 grid to either the anode or the cathode of the stimulator, leading to bipolar stimulations. When different electrode pairs were selected, perceived haptic sensation can be altered due to the change in the recruited sensory axons [27,28].…”

“…The stimulation parameters were controlled using a custom MATLAB interface, which could control the output current of a charge-balanced biphasic square wave stimulus in real time (figure 1(B)). A pulse width of 200 μs and a pulse frequency of 150 Hz were selected based on earlier studies [27,28].…”

“…Previously, a 2 × 8 electrode array was placed along a subject's upper arm. The electrode array stimulation has been shown to activate selective sets of afferent fibers in the proximal segments of the median and ulnar nerves [27,28]. Spatially and amplitude modulated sensations can be perceived by the participants at distinct regions of their hands [27].…”

Object Shape and Surface Topology Recognition Using Tactile Feedback Evoked through Transcutaneous Nerve Stimulation

“…1B) were delivered. Although pulse width, frequency, and dual stimulation delay were adjustable, these parameters were fixed at 200 μs, 150 Hz, and 3.33 ms, respectively, based on previous studies [22], [23].…”

“…Distinct axon recruitment produces spatially distinct sensation on the palm of the hand. Spatially separated sensations from different electrode pairs can also be directly summated using concurrent multi-channel stimulation, forming complex sensation patterns [23]. Building on this approach, two concurrent stimulation trains were used to target the median and ulnar nerve bundles, which generated individually modulated sensation at different fingers.…”