Doctor of Philosophy, Case Western Reserve University, 2020, Biomedical Engineering

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, (open full item for complete abstract)

Committee: Ronald Triolo (Advisor); Dustin Tyler (Committee Chair); Bolu Ajiboye (Committee Member); Cenk Cavusoglu (Committee Member) Subjects: Biomedical Engineering

Doctor of Philosophy (PhD), Ohio University, 2023, Translational Biomedical Sciences

Anterior cruciate ligament (ACL) rupture is a common and debilitating knee injury occurring in young active populations and can lead to rapid development of osteoarthritis. Most individuals undergo reconstructive surgery to restore the mechanical stability of the joint in an attempt to preserve knee joint health and physical function. Unfortunately, despite reconstructive surgery, individuals demonstrate protracted recovery of postural stability, muscle strength, and other neuromuscular impairments. Rupture of the ACL may be considered a partial deafferentation injury, where the sensory afferents from the joint and ligament are disrupted from the central nervous system. Deafferentation is confounded with pain and joint inflammation, making it difficult to understand what the isolated contribution of joint deafferentation to neuromuscular deficits are. Cross-sectional neuroimaging data suggests that widespread whole brain plasticity occurs after ACL reconstruction (ACL-R). However, the isolated effect of deafferentation to whole brain plasticity or physical performance is unknown. Integrating a novel model for knee joint deafferentation in healthy individuals, our findings suggest that joint afferents may contribute to the resting-state functional connectivity of multisensory integration regions with the whole brain. Additionally, physical function on postural stability in the presence of joint deafferentation may be preserved secondary to differences in resting state functional connectivity. We demonstrate a similar phenomenon in those with ACL-R, where individuals appear to be able to preserve physical function on proprioception and dynamic stability tasks through visual-cognitive 4 function and associated neural activity. Collectively, this work expands the current literature by exploring multisensory integration neuroplasticity after knee joint deafferentation, and associated visual-cognitive compensation strategies. Future work should aim (open full item for complete abstract)

Committee: Dustin Grooms (Advisor); Janet Simon (Advisor); Jed Diekfuss (Committee Member); Christopher France (Committee Member); Scott Monfort (Committee Member); Brian Clark (Committee Member) Subjects: Neurosciences; Physical Therapy; Rehabilitation

Doctor of Philosophy, Case Western Reserve University, 2021, Biology

Many animal taxa possess inertial sensory systems that aid in postural control via networks of stabilizing equilibrium reflexes. Flying insects typically make use of their multifunctional antennae and sensory feedback from their wings to fulfill this role, but in the true flies (order Diptera), the hindwings have evolved into specialized organs called halteres that are dedicated to this function. Like wings, the small aerodynamically-inert halteres beat up and down during flight under the control of a suite of power and steering muscles, maintaining a precise phase relationship with the forewings. Gyroscopic forces that arise from body rotations are detected by the primary sensory afferents of halteres—superficial mechanosensory neurons called campaniform sensilla. These specialized cells project to wing- and head-steering motoneurons, either directly or via interneurons, and mediate fast reflexes that are essential for flies to remain in the air. Descending projections from the visual system target the same motoneurons, and direct their own set of optomotor reflexes, raising the question of how information from these two sensory systems are combined by their shared nervous system elements to produce motor output. Using tethered flight behavioral experiments, we provided fictive gyroscopic information to the halteres using a novel electromagnetic stimulation method. The resultant haltere-evoked wing amplitude responses were found to sum linearly with those evoked by concurrently-provided visual information, whereas head movement responses combined information from the two sense modalities in a nonlinear fashion. Sensory coding for haltere-mediated head and wing reflexes is dependent upon haltere-wing phase synchrony and the accompanying baseline “metronomic” input from haltere campaniform sensilla. Bilateral haltere ablation renders flies incapable of precisely modulating the amplitude of their wing steering outputs and impairs head and wing optomotor responses. We (open full item for complete abstract)

Committee: Jessica Fox (Advisor); Hillel Chiel (Committee Member); Kathryn Daltorio (Committee Member); Mark Willis (Committee Member); Yolanda Fortenberry (Committee Chair) Subjects: Biology; Biomechanics; Neurobiology; Neurosciences

Doctor of Philosophy, The Ohio State University, 2019, Music

This dissertation is a cognitive ethnomusicological investigation regarding how each individual creates his or her own world via different musical behaviors. The goal of this thesis is to contribute to a model of our sense of time and space from an interdisciplinary perspective. There is a long tradition that we use two cognitive constructs, `time' and `space', when talking about the world. In order to understand how we humans construct our own worlds cognitively via music-making, I first distinguished two behaviors in music performance (singing vs. instrument playing). I looked at how the different modes of music-making shape our body in a distinctive way and modifies our perception of time and space. For the cognitive sections (chapters 2 & 3), I discussed not only building blocks of temporal experience but also features of space pertaining to the body. In order to build a comparative perspective (chapter 4), I examined various ancient understandings of time and space in different cultures. In terms of music evolution (chapter 5), I looked at the transformative power of music-making and speculated about potentially different modulatory processes between singing and instrument playing. The discussion in the cognitive sections provided the basic ideas for my `Hear Your Touch' project consisting of two behavioral experiments (chapter 6). I focused not only on two elements of temporal experience: 1) event detection, and 2) perception of temporal order, but also on several elements of spatial experience: 1) body space, 2) audio-tactile integration, and 3) space pertaining to hands. Both simple reaction time and temporal order judgment experiments provide supporting evidence for differences in spatiotemporal processing between musicians and non-musicians as well as between vocalists and instrumentalists. The simple reaction time experiment suggests that instrumental musical training contributes to enhanced multisensory integration through co-activation. The temporal o (open full item for complete abstract)

Committee: Will Udo (Advisor); Bishop Georgia (Committee Member); Boone Graeme (Committee Member) Subjects: Cognitive Psychology; Comparative; Evolution and Development; Music; Philosophy of Science