| Popis: |
Over one million individuals in the United States have a lower-limb amputation. Though locomotion is a sensorimotor process, no commercially available prostheses offer somatosensory feedback, and amputees continue to face locomotor challenges. Recent studies have demonstrated that electrically stimulating the residual nerves of amputees can elicit somatosensory percepts referred to the missing limb. Though peripheral nerve stimulation (PNS) takes advantage of the existing neural pathways that carry sensory information from the amputated limb to the brain, neural stimulation does not activate these afferent fibers in the same manner as physically-applied tactile stimuli. We hypothesized that these differences in neural activation may cause PNS-evoked sensation to be perceived differently than natural touch with respect to temporal synchrony and multisensory integration. In Aim 1, we found that the processing time and temporal sensitivity were not different between PNS-evoked and natural somatosensation. The similarity in visuotactile synchrony provided further evidence that PNS-evoked sensations are processed in broadly the same way as natural touch. In Aim 2, we established that much like natural somatosensation, vision and postural manipulations could reinforce PNS-evoked somatosensation. This multisensory integration had not been previously demonstrated and it is important for sensory neuroprostheses, which will be used in diverse environments with various sensory resources.The findings from Aims 1-2 demonstrated that PNS-evoked and natural somatosensation have similar properties, but did not guarantee that the body would utilize the sensory information accordingly. In Aim 3, we showed that amputees utilized PNS-evoked plantar sensation while performing a challenging locomotor task, revealing a significant and immediate benefit of somatosensory feedback to amputees. The use of a sensory-enabled prosthesis did not change the amputees’ locomotor strategies, which indicated that longer-term therapeutic benefits might require a longer familiarization period with the device. PNS allowed us to decouple sensory stimuli in a way that is not ordinarily possible, enabling probing of the underlying characteristics of multisensory integration. This dissertation lays the groundwork for future studies with additional target populations. Both trans-femoral and bilateral amputees are missing more sensory resources than unilateral trans-tibial amputees, and could benefit substantially from restoring balance resources, such as somatosensation. |
