Spinal cord injury results in life-long damage to sensory and motor functions. Recovery from these injuries is limited and often insufficient because the lack of stimulation from supraspinal systems results in further atrophy of the damaged neural pathways. Current studies have shown that repeated sensory activity obtained by applying stimulation enhances plasticity of neural circuits, and in turn increases the ability to create new pathways able to compensate for the damaged neurons. Functional electrical stimulation has been proven to show success in this form of rehabilitation, but it has its limitations. Stimulating neural pathways with electricity results in also stimulating surrounding neurons and muscle tissue. This results in attenuation of the intended effect. The use of optogenetics mitigates this issue, but comes with its own complications. Optogenetics is a growing method of neural stimulation which utilizes genetic modification to create light activated ion channels in neurons to allow for activation or suppression of neural pathways. In order to activate the neurons, light of the appropriate wavelength must be able to penetrate the nerves. Applying the light transcutaneously is insufficient, as the skin and muscle tissue attenuate the signal. The target nerve may also move relative to an external point on the body, creating further inconsistency. Specifically in the case of using a rat model, an external object will be immediately removed by the animal. This thesis seeks to address this issue for a rat model by designing a nerve cuff capable of both optical and electrical stimulation. This device will be scaled to fit the sciatic nerve of a rat and allow for both optical activation and inhibition of the neural activity. It will be wired such that each stimulus may be operated individually or in conjunction with each other. The simultaneous stimulation is required in order to validate the neural inhibition facet. The circuit itself will be validated through the use of an optical stimulation rig, using a photoreceptor in place of an EMG. The application of the cuff will be verified in a live naive rat. Aim 1: Design and build an implantable electrical stimulation nerve cuff for the sciatic nerve of rats. An electrical nerve cuff for the sciatic nerve of a rat will be designed and assembled such that it is able to reliably activate the H-reflex. For it to be used in a walking rat, the cuff must be compatible with a head mount in order to prevent the rat from being able to chew at the wiring or their exit point. The cuff will be controlled through a Matlab program that is able to output specified signals and compare these outputs directly with the resultant EMG inputs. Aim 2: Implement LEDs onto the cuff and perform validation experiments. Light delivery capability will be added to the cuff through the use of LEDs. The functionality of the cuff will be validated through tests on naive rats. If successful, only an electric stimulation will result in a muscle twitch. An optical stimulation should result in no twitches, which would then validate that no current is leaking from the nerve cuff, given that the rat does not express any light sensitive protein channels. Ultimately, with a rat expressing ChR2 opsins on the sciatic nerve, an activation of the nerve using a blue light of wavelength 470nm will result in activating an h-wave without an m-wave when optically stimulated. Similarly, using the nerve cuff with a rat expressing ArchT opsins will result in suppressing the h-wave from an electric stimulation once the sciatic nerve is illuminated with green light of a wavelength of 520 nm. / Bioengineering

published_or_final_version / Speech and Hearing Sciences / Doctoral / Doctor of Philosophy

Call number: LD2668 .T4 1986 W32 / Master of Science / Physical Education, Dance, and Leisure Studies

ABSTRACT: Whiplash-associated disorders are a common occurrence. Physiotherapy rehabilitation of such disorders include, among others, improving the recruitment ability of the deep cervical flexor muscles. Cervical proprioception, which has recently gained attention, is not commonly addressed. Evidence points to a possible link between cervical proprioception and deep cervical flexor recruitment ability. This study aimed to determine whether such a correlation exists. This is significant as it highlights the role that recruitment training of the deep cervical flexors has on cervical proprioception. A correlation study design was employed that involved 29 patients with whiplashassociated disorders. They were tested in their ability to perform the cranio-cervical flexion test and Revel’s test for proprioception. Linear regression was employed to interpret the results. This study concluded that a correlation exists between the ability to perform the craniocervical- flexion test and cervical proprioception.

Subacromial impingement accounts for significant burdens on the economy and individual quality of life. The development and progression of this disorder is thought to be related to overuse; however, little is known regarding biomechanical factors such as scapular kinematics, shoulder muscle recruitment and joint proprioception with respect to this disorder. The high degree of variability between individuals on these biomechanical measures limits our ability to make inferences behind the development of shoulder impingement. Here, biomechanical factors associated with impingement are investigated using within-subjects designs in order to reduce this inherent variability. Using modern clinical techniques, this dissertation is applicable towards treatment of shoulder impingement as well as scientific understanding of motor control and function in the presence of pain. This dissertation includes previously published and un-published co-authored material.

Background: Diabetic peripheral neuropathy (DPN) is diagnosed clinically as a loss of sensation in the feet and affects over 2 million people in the UK. One of the functional effects of DPN is a decrease in standing stability giving rise to a risk of falls. In an attempt to stabilise in the mediolateral direction, people with DPN frequently walk with a wider base of support and stand with a larger stance width. This is often seen in the elderly and is not always beneficial for stability contributing to falls risk. Standing balance requires the integration of sensory information from somatosensory, vestibular and visual systems. Alterations in distal sensory input may result in a re-weighting of the effectiveness of remaining sensations in mediating a stabilising postural response; termed sensory re-weighting. Alterations in posture such as adopting a wider stance width and wearing Ankle Foot Orthoses (AFOs) may also affect sensory input as well as altering the mechanics of the ankle and hip joints. The impact of distal sensory loss on the sensory control of balance in people with DPN compared to the healthy population is unknown. Moreover, it is not known whether standing balance or the sensory control of balance is affected by the adoption of an increased stance width and wearing (AFOs) that restrict mediolateral ankle motion. A better understanding of the mechanisms underlying balance dysfunction in diabetic peripheral neuropathy and how it might be manipulated could inform the development of future interventions to improve balance. Aim: To explore the effects of ankle foot orthoses and stance width on standing balance and the sensory control of mediolateral balance in people with DPN and healthy controls. Objectives: To assess how mediolateral postural stability and the sensory control of balance is affected by (a) AFO use and alterations in stance width in healthy participants (study 1) (b) acute distal sensory loss in healthy participants (study 2) (c) chronic sensory loss in people with DPN and how this in turn is modulated by AFO use and alterations in stance width (study 3). Methods: Postural stability and the response to selective muscle vibration that stimulates muscle spindle afferents was measured by 3D motion analysis. Study 1 investigated the effects of stance width and AFOs on postural sway and the response to selective hip proprioception stimulation induced by vibration of the hip abductors in healthy participants. Study 2 investigated the effect of an acute reduction of somatosensory information induced by cooling in healthy participants on the response to ankle evertor and hip abductor vibration. This provided a model of the acute effects of sensory loss. Study 3 compared healthy people with people with chronic DPN. It investigated the impact on stance stability and whether there was a change in the postural response (gain) to ankle evertor and hip abductor vibration. It further explored the effect of altering the stance width and wearing an AFO on stability and the postural response to hip abductor vibration. Results: Study 1: In healthy controls postural sway was significantly reduced when wearing an ankle foot orthoses and when standing at wider stance widths. Whilst this was also seen during balance perturbation, trunk motion increased at larger stance widths. This could be the result of the AFO restricting ankle motion and affecting the interpretation of the hip vibratory input by the postural control system. Study 2: Experimental reduction in distal sensation by cooling resulted in a reduction in postural responses to ankle evertor muscle vibration. Conversely postural responses at the level of the hip, to proximal (hip) muscle vibration, significantly increased. Study 3: Baseline sway velocity was higher in people with DPN compared to healthy controls. Postural strategies were modified in the DPN group, with increased motion at more proximal segments of the shoulder and head. In both groups, AFO and stance width significantly reduced baseline sway velocity, and the size of postural responses (translations) to hip abductor muscle vibration. Conclusion: Alterations in stance width and the use of AFOs can affect postural sway and the response to selective proprioceptive stimulation. Whilst acute reductions in distal sensory loss are associated with sensory re-weighting of distal and proximal proprioceptive information this is not seen in people with chronic DPN, possibly resulting from long term adaptive changes in the multi-sensory control of balance. Novel differences were found in postural strategies between healthy and DPN groups. The increase in head and trunk motion in people with DPN may have a negative impact on visual acuity and therefore a risk factor for falls. In people with diabetic peripheral neuropathy AFOs and increased stance width led to a reduction in postural response size and postural sway. The effect of AFO on sway velocity was more pronounced in those with DPN at smaller stance widths. Clinically this suggests that an AFO could be used in those with diabetic peripheral neuropathy to slow down the velocity of sway and increase stability.

Fifteen female subjects ages 13-16 were recruited to determine if differences exist in knee joint proprioception, with and without application of a neoprene knee sleeve (NKS), when performing reproduction of target angle test (RTA), movement sensation test (MS) using a Biodex testing machine, and single leg standing test. Ten subjects had not worn a NKS and five subjects had worn a NKS. After completing all IRB approved documentation subjects underwent a test trial of each of the three testing methods. Subjects were randomly assigned a number that determined if the subject began the test trial with or without a NKS. Three starting angles were identified for the MS and the RTA tests; error was used to determine accuracy in both tests. The single leg stand tests consisted of the test subject closing her eyes and standing for as long as possible, no longer than five minutes, on her dominant leg.

Abstract not available

Osteoarthritis and ageing have been shown to induce changes in the number and health of peripheral mechanoreceptors. Whilst position and movement awareness in the osteoarthritic knee have been studied extensively, little work to date has been produced on muscle force awareness in this subject group. Poor force acuity may contribute to muscle and joint pain and dysfunction, and additionally hinder rehabilitation efforts in an osteoarthritic population. Overestimation of the muscles forces required for a given task, resulting in greater joint compression forces, may aggravate and inflame osteoarthritic symptoms. Underestimation of required muscle forces may amplify existing joint instability, increasing the risk of injury in an osteoarthritic population. Additionally, both under and overloading of muscles during the rehabilitation process can delay the return to full function after injury.When regarding the neurological process of force coding, current debate centres on the relative importance of centrally generated motor command mediated 'sense of effort' versus the peripheral mechanoreceptor signalled 'sense of tension' as the dominant coding process, with central mechanisms favoured in the majority of studies published to date. The purpose of this study was to investigate muscle force awareness in the knee extensors and flexors and hands of subjects with and without knee joint osteoarthritis. Twenty one subjects with knee joint osteoarthritis and 23 age and gender matched subjects with no known knee pathology were evaluated. All subjects performed ipsilateral isometric force estimation and force matching tasks, at levels scaled to individual maximum voluntary capacity (MVC). Errors in estimation and matching acuity were normalised to reference targets (comparison force/reference force) giving a relative score (RS) to allow comparison across submaximal force levels with RS less than 1.0 indicating that subjects produced insufficient force and vice versa.Maximal voluntary capacity tests revealed significantly lower (p<0.05) peak knee extension torque (111.2 Nm versus 145.3 Nm), but similar peak knee flexion torque (46.1 Nm versus 45.4 Nm for osteoarthritis and control subjects respectively). A pattern of overestimation at low reference levels and underestimation at high reference levels was demonstrated by all subjects. In the lower limb, force appreciation differed significantly between muscle groups regardless of knee condition, with knee extensors demonstrating greater overall accuracy than knee flexors. There was a significant difference (p<0.05) in force estimation ability and a trend to significance (p=0.066) for force matching acuity across groups at the 10% MVC test level. A significant (p<0.05) group difference in grip force estimation ability between the lowest and highest target levels was demonstrated.It can be concluded that there are small differences in force acuity in osteoarthritis subjects at lower submaximal force targets when compared to healthy age matched peers. The notion of information redundancy, whereby no new proprioceptive inputs, regardless of origin, are able to effect an improvement in force acuity in a given situation has been demonstrated in previous studies that reported relatively stable force matching acuity at forces between 30% and 60% of maximal capacity. The poor comparative force perception demonstrated in this study by the osteoarthritis group at the lower submaximal test levels supports the notion that centrally generated copies of motor commands do not provide sufficient data to adequately encode force magnitude at low levels of force generation, evoking a greater reliance data received from peripheral mechanoreceptors. This has significant implications for this subject group given that the majority of daily tasks require only low levels of force generation. Given that perceptive acuity in a variety of sensory modalities has been shown to improve with training there may be a role for force perception training in older adults with osteoarthritis.

This thesis investigates the differential effects of muscle fatigue on center of pressure (COP) sway and associated central processes (attentional demands and sensory re-weighting) in older compared with young adults. More specifically, we first sought to determine whether the effect of muscle fatigue on unipedal stance was greater during a dual-task in older versus young adults, and second, to determine whether the effect of muscle fatigue on bipedal stance was greater in a condition with less reliable proprioceptive information in older versus young adults. Our main results show that with different muscle groups fatigued (ankle or hip) and postural tasks with varying difficulty (unipedal stance or bipedal stance on compliant surface), young adults increased their COP sway displacement and velocity with muscle fatigue, but not the associated attentional demands. When the central nervous system needed to increase the weight of the vestibular inputs due to sensory information being less reliable at the ankle joints from standing on a compliant surface (peripheral somatosensory information), COP sway displacement and velocity in young adults were greater with ankle muscle fatigue. We also found that healthy older adults were able to compensate for muscle fatigue just as well as young adults when visual information was available during a unipedal stance or when visual information was not available during a bipedal stance on a firm surface. However, when standing on a compliant surface, older adults showed a greater increase in COP sway displacement compared to young adults and increased attentional demands when visual information was not available during a bipedal stance. Our results suggest that healthy young and older adults are able to compensate for ankle muscle fatigue to limit postural control alterations during quiet standing under different conditions, and that the extent of postural control alterations largely depends on the tasks performed. The compensation strategies may be less efficient for older adults with less reliable proprioceptive information and without vision. Thus, a frailer group of older adults, with already reduced proprioception and/or reduced vision could possibly have more difficulty to efficiently use the same compensation strategies, and may be more at risk of falling when fatigued.