Intraneural sensory feedback: from the assessment of current clinical usability to the development of novel neural interfaces

To promote the application of neural prosthesis in amputees, we developed a closed-loop system to provide amputees with sensory feedback. Sequentially, we developed a neural electrode to reduce surgery time and implantation complexity. The lack of afferent feedback in commercially available prosthesis makes patients rely on visual feedback. The quality of life can, therefore, not be restored to its full potential. Intraneural electrodes were implanted in three trans-radial amputees to provide them with sensory feedback. A closed-loop system, including a neurostimulator and a myoelectric hand prosthesis, allowed patients to receive sensory feedback while manipulating objects. Single and multi-channel stimulation were evaluated. Frequency and amplitude modulation were compared. All perceived sensations were recorded and analyzed. After the completion of the clinical studies, a neural electrode was developed to reduce the implantation time and complexity. A quick-to-implant guidance system was developed. The electrodes have been tested in acute experiments, in four pigs, in vivo. Human subjects reported different types of stimulation-induced sensations for most of the trials. They successfully applied sensory feedback with and without visual feedback. Multi-channel stimulation showed to provide sensory facilitation. Combining single channels provoked a linear combination of single-channel evoked sensations. Frequency and amplitude modulation suggested amplitude modulation to be more effective. The newly developed electrode was faster and easier to implant compared to previous approaches. Sensory feedback in amputees showed to be an auspicious approach to restore the quality of life. To promote commercial application, a fully implantable system would be necessary, combining the here presented strategies.