PHD Thesis Defense Neural Engineering
Sedona Cady
Ph.D. Candidate
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Department of Biomedical Engineering
Cleveland, OH
Thesis Advisor: Dustin Tyler, PhD
Location NORD 356
ABSTRACT
Individuals with upper limb loss often find commercial prostheses unsatisfactory due to factors such as unreliable control and lack of sensory feedback, contributing to reduced function and worsened psychosocial experiences. Implanted nerve stimulation and myoelectric recording systems offer promising solutions by providing sensation and more advanced prosthetic control. However, several challenges hinder translation of these technologies, including percutaneous lead maintenance, bulky external processors, a limited number of implanted electrode channels, and a narrow focus on either sensory feedback or myoelectric sensing, rather than both features. Additionally, the benefits of implanted bidirectional neuroprosthetic systems compared to currently available commercial prostheses remain largely unexplored.
To create a more complete sensorimotor restoration system, our team developed a non-percutaneous, implanted somatosensory electrical neurostimulation and sensing (ISENS) system, featuring bidirectional stimulation and sensing, wireless communication, and an increased electrode channel count. The central hypothesis was that ISENS would enhance sensory perception, psychosocial experiences, and function for upper limb prosthesis users.
Initial feasibility testing in two individuals with upper limb loss confirmed ISENS long-term stability and validated bidirectional high degree-of-freedom (DOF) prosthetic control with sensory feedback. The ISENS system’s increased implanted channel count improved high DOF myoelectric control, expanded sensory coverage across the hand, and increased the number of distinct percept locations, enabling diverse sensory feedback. Beyond the lab environment, long-term home use of ISENS with a bidirectional prosthesis led to significant improvements in psychosocial outcomes, including social interaction and embodiment, compared to a clinically prescribed commercial prosthesis. Although the tendency to favor the sound arm over the prosthesis did not change, functional dexterity and activities of daily living performance improved, likely facilitated by the high DOF prosthetic control.
This work validates ISENS as a fully implanted bidirectional neuroprosthetic system that enhances sensory perception and provides meaningful psychosocial and functional benefits to prosthesis users. These findings represent significant progress toward clinical translation of implanted sensorimotor interfaces to overcome limitations of conventional prostheses and ultimately improve the lives of individuals with limb loss.