Neuromorphic hardware for somatosensory neuroprostheses

Abstract

In individuals with sensory-motor impairments, missing limb functions can be restored using neuroprosthetic devices that directly interface with the nervous system. However, restoring the natural tactile experience through electrical neural stimulation requires complex encoding strategies. Indeed, they are presently limited in effectively conveying or restoring tactile sensations by bandwidth constraints. Neuromorphic technology, which mimics the natural behavior of neurons and synapses, holds promise for replicating the encoding of natural touch, potentially informing neurostimulation design. In this perspective, we propose that incorporating neuromorphic technologies into neuroprostheses could be an effective approach for developing more natural human-machine interfaces, potentially leading to advancements in device performance, acceptability, and embeddability. We also highlight ongoing challenges and the required actions to facilitate the future integration of these advanced technologies.

Fig. 1. Neural prostheses for sensory feedback restoration.

The main building blocks of a neural prosthesis for the somatosensory system are the sensing block, the computing block, and the stimulating block. Sensing technology (e.g., wearable tactile sensors) has to be embedded in the robotic prostheses in order to extract all the relevant physical interactions with the external world. Then, the computing block, composed of the neuromorphic technology, has to translate the sensors’ readouts into electrical patterns of stimulation using biomimetic encoding algorithms. Finally, the stimulating block has to inject currents in the nervous tissue, through implantable electrodes, able to evoke natural neural activations, allowing for natural and informative sensations. A portion of the illustration is adapted from ref. .

Fig. 2. Biomimetic approach for encoding sensory information via neural stimulation.

A The whole pipeline of neural stimulation patterns for somatosensory feedback restoration based on non-biomimetic design and B based on biomimetic design. In the latter case, the stimulation parameters, such as frequency, amplitude, and stimulating channels are modulated in order to evoke natural patterns of neural activation. A portion of the illustration is adapted from ref. .

Fig. 3. Biomimicry implemented in a neuro-robotic device thanks to neuromorphic hardware.

The complete design of a closed-loop biomimetic neuro-robotic prosthesis exploiting neuromorphic hardware is depicted. The pressure events under the prosthetic foot are sensed by the wearable sensors embedded in artificial skin. The stream of information from these sensors is the input for the neuromorphic chip that converts them into bio-inspired neural stimulation patterns resembling natural somatosensory processing. The co-modulations of the neurostimulation parameters and the channels of the implanted neural interfaces will allow the evoking of natural patterns of activation in the residual nervous system of the user. The electrically evoked sensation will be natural and informative allowing for the maximal exploitation of the robotic prosthesis in the sensory-motor loop. A portion of the illustration is adapted from ref. . Grafica_001 © 2021 by Pietro Comaschi is licensed under CC BY 4.0.