Providing proprioceptive information through biomimetic multi-electrode stimulation patterns

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Project Summary The overall goal of this project is to provide proprioceptive information to tetraplegic patients and amputees, thus augmenting current efferent interfaces. Restoring proprioception is vital for restoring motor control, evidenced by extreme movement impairments in individuals with proprioceptive loss. Despite this, proprioceptive interfaces have received less attention and have had less success than tactile interfaces, which can provide contact location information to a spinal cord injured patient through intracortical microstimulation (ICMS). Developing techniques to provide proprioceptive information during movement remains a critical and unsolved problem. Tactile interfaces have found success by mimicking the localized response recorded in primary somatosensory cortex evoked by punctate stimuli. In contrast, limb movements evoke a complex spatial pattern of neural activity across area 2 of primary somatosensory cortex (S1). It may be that recreating this spatial pattern of activity will elicit naturalistic sensations of limb movement. I propose to use multi-electrode ICMS (mICMS) to do this. I expect this biomimetic approach to provide conscious and subconscious proprioceptive information, both of which are vital for restoring motor control. The effect of this biomimetic approach will be compared to nonbiomimetic approaches in two Specific Aims. In Aim 1, I will compare the efficacy of these stimulation approaches for providing conscious perception of limb movements, which will reduce phantom limb pain and improve prosthesis satisfaction. Here, monkeys will report the direction of perceived hand movement by reaching in that same direction. I will test these stimulation approaches in naturalistic cases and after monkeys learn mappings between mICMS and reach direction. In Aim 2, I will evaluate whether mICMS can provide the feedback required to update an ongoing reach, a critical component of proprioception for which visual feedback is insufficient. While reaching, either a mechanical or virtual perturbation delivered through a brief train of mICMS will be applied to the monkey. During mechanical perturbation trials, monkeys will need to correct their reach to hit the target. On mICMS trials, I expect monkeys to correct their reach as if their hand were physically moved. These two aims provide a complimentary approach to restoring proprioception, as both conscious perception of limb movements and rapid feedback required to update reaches are vital components of proprioception.