The NIH neuroprosthesis program has fostered so much success in the area of cortically controlled neuroprostheses that the FDA has approved multiple human trials to test the safety and efficacy of cortical implants for brain machine interfaces (BMI). An important application of BMI technologies is the direct cortical control of prosthetic limbs. However, a critical gap in this effort is the lack of somatosensory feedback which is needed to support proprioception and tactile sensations for the artificial limb. We propose that multichannel microstimulation of primary afferent neurons in the dorsal root ganglia (DRG) would provide a viable and preferred route for restoring natural sensation of limb posture, movement, force, and tactile sensation. This approach is similar, in principle, to that of the cochlear implant, which uses multichannel electrical stimulation of auditory nerves to restore hearing to people with profound deafness. The primary objective of the proposed research is to create a new animal (cat) model for developing a neural interface with somatosensory afferent neurons in the cervical DRG. Our approach builds on our previous success with obtaining acute and chronic single unit recordings from large numbers of primary afferents in the lumbar DRG of cats (Stein et al. 2004; Weber et al. 2006). The proposed model will serve two important goals: 1) the development of a somatosensory neural interface for the neuroprosthetic applications described above and 2) basic investigations into the sensory feedback control of arm movement. It is useful to pursue these goals in parallel, because a comprehensive understanding of the role and nature of sensory feedback related to limb-state will guide the design and implementation of neuroprostheses that interface directly with the nervous system for feedback and control. The goal of this proposal is to develop a technique for providing proprioceptive sensations to users of prosthetic limbs using multichannel electrical microstimulation of primary afferent neurons in the dorsal root ganglia (DRG). This approach is similar, in principle, to that of the cochlear implant which uses patterned electrical stimulation of auditory nerves to restore hearing to people with profound deafness. These experiments will quantify the extent to which artificial electrical stimulation of peripheral afferents can drive natural patterns of neuronal activity in somatosensory regions of the brain. ? ? ?
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