Biomimetic multi-channel microstimulation of somatosensory cortex conveys high resolution force feedback for bionic hands

Introduction: The restoration of tactile feedback is critical for the functionality of brain-controlled bionic hands, an emerging area of research in functional neurosurgery and neuroengineering. This study focuses on human intracortical microstimulation (ICMS) of the somatosensory cortex (S1) to restore tactile feedback related to contact force in bionic hands of spinal cord injury patients. The intensity of stimulation, reflecting the output of force sensors on the bionic hand, modulates the perceived magnitude of sensation, which is vital for users to handle objects effectively and perceive the subtleties of touch.

Methods: Three human participants with implanted microelectrode arrays in S1 were involved in the study to assess the dynamic range and precision of ICMS-based force feedback. We measured sensation magnitude as a function of ICMS amplitude to understand how changes in stimulation intensity affect perception. Participants were also tested on their ability to distinguish between different levels of intensity. We investigated the effects of biomimetic ICMS-trains, designed to emulate natural tactile sensation patterns, and multi-channel stimulation to enhance feedback fidelity. Additionally, we integrated biomimetic multi-channel ICMS into a bionic hand to evaluate its effectiveness in a compliance discrimination task.

Results: Our findings indicated that multi-channel biomimetic ICMS elicited stronger and more distinct sensations compared to single-channel stimulation. In the compliance discrimination task, participants using biomimetic multi-channel feedback were able to discern differences with greater accuracy than with single-channel linear feedback, pointing towards a more nuanced force feedback system [Wilcoxon, Z = -3.05, p < 0.01].

Conclusion : Biomimetic multi-channel ICMS significantly enhances force feedback fidelity in bionic hands, providing sensations that more closely resemble natural touch sensitivity. This approach represents a substantial advancement in neuroprosthetic development, potentially offering users of bionic hands a level of sensory feedback that approaches the complexity and richness of natural touch, thereby improving the overall utility and user experience of prosthetic limbs.