Effects of Sensorimotor Perturbations on Balance Performance and Electrocortical Dynamics

Humans must frequently adapt their posture to prevent loss of balance. Such balance control requires complex, precisely-timed coordination among sensory input, neural processing, and motor output. Despite its importance, our current understanding of cortical involvement during balance control remains limited by traditional neuroimaging methods, which are stationary and have poor time resolution. High-density electroencephalography (EEG), combined with independent component analysis, has become a promising tool for recording cortical dynamics during balance perturbations due to its portability and high temporal resolution. Additionally, recent improvements in immersive virtual reality headsets may provide new rehabilitative paradigms, but the effects of virtual reality on balance and cortical function remain poorly understood. In my first study, I recorded high-density EEG from healthy, young adult subjects as they walked along a beam with and without virtual reality high heights exposure. While virtual high heights did induce stress, the use of virtual reality during the task increased performance errors and EEG measures of cognitive loading compared to real-world viewing without a headset. In my second study, I collected high-density EEG from healthy young adults as they walked along a treadmill-mounted balance beam to determine the effect of a transient visual perturbation on training in virtual reality. Subjects in the perturbations group improved comparably to those that trained without virtual reality, indicating that the perturbation helped subjects overcome the negative effects of virtual reality on motor learning. The perturbation primarily elicited a cognitive change. In my third study, healthy, young adult EEG was recorded during physical pull and visual rotation perturbations to tandem walking and tandem standing. I found similar electrocortical patterns for both perturbation types, but different cortical areas were involved for each. In my fourth study, I used a phantom head to validate EEG connectivity methods based on Granger causality in a real-world environment. In general, connectivity measures could determine the underlying connections, but many were susceptible to high-frequency false positives. Using data from my third study, my fifth study analyzed corticomuscular connectivity patterns following sensorimotor balance perturbations. I found strong occipito-parietal connections regardless of perturbation type, along with evidence of direct muscular control from the supplementary motor area during the standing perturbation response. Taken together, the work presented in this dissertation greatly expands upon the current knowledge of cortical processing during sensorimotor balance perturbations and the effect of such perturbations on short-term motor learning, providing multiple avenues for future exploration.PHDBiomedical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/147615/1/stepeter_1.pd

Waterfowl Ecology and Utilization of Uinta Mountain Water Areas

Waterfowl utilization was recorded by observing study units at different elevations from the time water areas were thawed in the spring until they were frozen in the fall. Sixteen species of waterfowl were observed in the Uinta Mountain; mallards, green-winged teal, pintails, and ring-necked ducks were breeders. Ninety-eight percent of all waterfowl observed were below 10,000 feet. Waterfowl numbers were highest during migratory periods and lowest in the breeding season. Adult waterfowl were observed most often on natural water areas and beaver ponds greater than one acre. Water areas at lower elevations had high indices of aquatic invertebrates and contained aquatic plants with high seed producing capabilities whereas water areas at high elevations had little water-fowl food

Administration of Utah\u27s Governmental Immunity Act by Utah\u27s School Districts

Purpose Since the Utah Governmental Immunity Act went into effect on July 1, 1966, the experience of Utah\u27s school districts under the law was not known. For the purpose of determining the experience of Utah\u27s districts in administering the law and to determine the adequacy of the law, this study was undertaken. Procedures To accomplish the purpose of this study, a questionnaire was sent to each of Utah\u27s 40 school districts. Instructions were sent with the questionnaire indicating that the writer would be making contact either by telephone or a personal interview to assist in filling out the questionnaire. A personal interview was conducted with 15 districts, and telephone contact was made with the remaining 25 districts. Additional information which could not be obtained from Utah\u27s school systems was obtained from insurance agents, legal advisors, and various other related sources

Power assist EVA glove development

Structural modeling of the EVA glove indicates that flexibility in the metacarpophalangeal (MCP) joint can be improved by selectively lowering the elasticity of the glove fabric. Two strategies are used to accomplish this. One method uses coil springs on the back of the glove to carry the tension in the glove skin due to pressurization. These springs carry the loads normally borne by the glove fabric, but are more easily deformed. An active system was also designed for the same purpose and uses gas filled bladders attached to the back of the EVA glove that change the dimensions of the back of the glove and allow the glove to bend at the MCP joint, thus providing greater flexibility at this joint. A threshold control scheme was devised to control the action of the joint actuators. Input to the controller was provided by thin resistive pressure sensors placed between the hand and the pressurized glove. The pressure sensors consist of a layer of polyester film that has a thin layer of ink screened on the surface. The resistivity of the ink is pressure dependent, so an extremely thin pressure sensor can be fabricated by covering the ink patch with another layer of polyester film and measuring the changing resistance of the ink with a bridge circuit. In order to sense the force between the hand and the glove at the MCP joint, a sensor was placed on the palmar face of the middle finger. The resultant signal was used by the controller to decide whether to fill or exhaust the bladder actuators on the back of the glove. The information from the sensor can also be used to evaluate the effectiveness of a given control scheme or glove design since the magnitude of the measured pressures gives some idea of the torque required to bend a glove finger at the MCP joint. Tests of this actuator, sensor, and control system were conducted in an 57.2 kPa glove box by performing a series of 90 degree finger bends with a glove without an MCP joint assembly, a glove with the coil spring assembly, and with the four fingered actuated glove. The tests of these three glove designs confirm the validity of the model

Everyday Lives of the Elderly: A Dimensional Analysis

Considerable dissension surrounds the number and composition of the domains comprising the daily lives of the elderly. The present study employs an array of biological, economic, political, social, and psychological data obtained from a house-to-house survey of elderly citizens to derive a mapping of dimensionality. Factor analysis of the data isolated eight domains: Poor Health, Disengagement, Self-Sufficiency, Female Aging, Meaningful Employment, Political Faith, Self-Starting, and Stoicism. External validation supported the factor solution and highlighted the impact of dietary and economic deficits on the problems of the aged

A preliminary structural analysis of space-based inflatable tubular frame structures

The use of inflatable structures has often been proposed for aerospace and planetary applications. The advantages of such structures include low launch weight and easy assembly. The use of inflatables for applications requiring very large frame structures intended for aerospace use are proposed. In order to consider using an inflated truss, the structural behavior of the inflated frame must be examined. The statics of inflated tubes as beams was discussed in the literature, but the dynamics of these elements has not received much attention. In an effort to evaluate the vibration characteristics of the inflated beam a series of free vibration tests of an inflated fabric cantilevers were performed. Results of the tests are presented and models for system behavior posed

Can we use conceptual spaces to model moral principles?

status: publishe