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The present dissertation investigates perceptual grouping and shape completion in motion in younger and older observers. The first set of experimental results, Chapter 2, provides a set of exploratory experiments which characterize the nature of a motion grouping task, uncovering accurate direction discrimination when the stimulus contains a cue for global grouping, but compelling illusory motion when the stimulus does not contain that cue. Chapter 3 builds on the findings of Chapter 2 by measuring biases in motion integration that lead to the illusory motion. Chapter 3 extends this paradigm into older adult observers, and explores various stimulus variants and tasks to add to the characterization of this effect. In Chapter 4 the concepts of grouping and motion perception are examined in the context of shape completion by measuring the accuracy of aspect ratio, size, and area discrimination in younger and older adults. Chapter 4 concludes that older adults are worse at discriminating characteristics of shapes, but are similarly affected by incomplete or occluded stimuli as younger adults. On the whole, the dissertation demonstrates several novel findings in the perceptual organization literature, and investigates many of these phenomena into older adults populations. Throughout the dissertation, a central theme concerns the concept of behavioural measurement of perceptual processes, and consequently many of the phenomena are studied using several types of measurements and tasks to ensure a complete picture of the perceptual experience. The current dissertation presents a novel and important addition to the current literature in perceptual grouping and shape completion. / Dissertation / Bachelor of Arts (BA) / The visual experience of a human observer is the result of perceptual processing of the brain. The current dissertation focuses on a subset of these processes that concern the grouping of segmented parts into a single shape, while those segmented parts are in motion. This type of visual experience occurs regularly, in situations where part of a visual scene is occluded such as when viewing a moving object through a window occluded by window blinds. In general, we measure an observer's ability to identify the sources of motion, and the ability to infer the shape of the grouped object. In each experiment, the physical stimulus is varied while observers complete tasks using this stimulus. The dissertation characterizes perceptual organization processes using a number of different tasks, stimuli and paradigms in both younger and older adults. Each experimental result characterizes the perceptual abilities of younger and older observers, contributing to the literature of visual perceptual organization in aging.

With the aging of the baby boom population and an increased life expectancy, individuals aged 65 years and older are the fastest growing segment of our population. Aging brings about changes in skeletal muscle such as reduced muscle strength and mass, as well as cellular deficits such as increased production of reactive oxygen species (ROS), and mitochondrial DNA (MtDNA) deletions and mutations. Muscle mass declines at a rate of 1-2% each year after the age of 50, leading to muscle weakness, functional impairments, loss of independence, and an increase in falls. Additional declines in muscle mass and reduced muscle strength may result in a lower resting metabolic rate, reduced lipid oxidative capacity, increased adiposity, and insulin resistance. The rising number of individuals aged 65+ will increase demands on health care and health care costs, possibly leading to inadequate public resources and less care for the aged. This large societal impact, coupled with the aging of our population, suggests a clear need for methods that will improve the aging phenotype to enhance functionality, quality of life, and overall health for our aging population. This investigation aspires to delve into a relatively unexplored area of aging research and evaluate potential means that could help improve the aging phenotype. The associated mitochondrial impairments, mitochondrial mediated apoptosis, and mitochondrial DNA (MtDNA) deletions and mutations that accompany aging lead to a decline in physical fitness and oxidative capacity, and exercise has been shown to reverse or help prevent many of these disturbances. Resistance exercise training (RT) is currently the most effective known strategy to stimulate skeletal muscle hypertrophy and increase strength. Strength gains after RT lead to an improvement in activities of daily living and quality of life. There is some evidence suggesting that RT may lead to increased antioxidant enzyme capacity, decreased ROS production and increased electron transport chain (ETC) function in older individuals. The present study will lay a foundation for future research and further developments in the area of RT, mitochondrial function and aging. / Ph. D.

Aging has been associated with numerous changes in the neuromuscular system. Age effects on muscular performance, however, have been addressed only in limited contexts in earlier research. The present work was conducted primarily to investigate age-related effects on muscle capacity (fatigue and endurance) during isometric and dynamic efforts. This work was also motivated by current theories on muscle fatigue as a potential risk factor for musculoskeletal disorders and recent demographic projections indicating a substantial increase of older adults in the working population. Four main experiments were conducted to investigate development of muscle fatigue during isometric and intermittent efforts in shoulder abduction and torso extension at different contraction levels. Two age groups were involved (n=24 in each), representing the beginning and end of working life. Findings from this study demonstrated that the older group exhibited slower progressions of fatigue, though the age effect was more consistent for the shoulder than the torso muscles. This implied a muscle dependency of the influence of age on fatigue. Several interaction effects of age and effort level were also observed, suggesting that both task and individual factors should be considered simultaneously in job design. The present investigation also sought to develop alternative electromyography (EMG)-based fatigue parameters for low-level isometric and dynamic contractions, two areas in which improvements are needed in the sensitivity and reliability of existing EMG indices. Several alternative EMG indices were introduced, derived from logarithmic transformation of EMG power spectra, fractal analysis, and parameter estimation based on a Poisson distribution. Potential utility of several of these alternative measures was demonstrated for assessment of muscle fatigue. / Ph. D.

Work-related musculoskeletal disorders (WMSDs), particularly overexertion injuries, represent a significant economic burden and involve substantial adverse personal outcomes. Two important contemporary changes in workforce demographics may be associated with an increase in the future incidence and cost of WMSDs. First, more than two-thirds of the US adult population is now either overweight or obese, a doubling of the prevalence of obesity over the past 30 years. Second, there has been a shift toward an older worker population, whose injuries often require more time away from work. Obesity and aging can modify job demands and affect worker capacity in terms of muscular and psychomotor function. However, there is a lack of empirical studies quantifying the work-relevant (or ergonomic) impacts related to task demands, capacities, and their potential imbalance. This research assessed obesity- and age-related differences in physical capacity by measuring localized muscle fatigue, endurance, and the effects of fatigue on psychomotor function. Three experiments were completed, progressing from controlled static to more complex intermittent and functional tasks. The work also examined whether obesity and age effects are modified by workplace/workstation configuration, specifically the extent to which body segment masses need to be supported. With obesity, strength was higher, but endurance time was lower, particularly for the more complex tasks. Interaction effects between obesity and age were seen in only a few measures across the studies and did not indicate a consistent effect. Outcomes of this research can facilitate the development of more effective (i.e., inclusive) guidelines to control WMSD risk and contribute to both proactive and reactive interventions to reduce excessive exposures to physical risk factors. Overall, the research goal is to help ensure that ergonomic guidelines and practice are appropriate (or are adapted) to accommodate the diverse and changing workforce. / Ph. D.

Falls due to slipping are a serious occupational concern. Slipping is estimated to cause 40-50% of all fall-related injuries. In 2011, falls resulted in 22% of injuries requiring days away from work. Epidemiological data indicates that older and obese adults experience more falls than young, non-obese individuals. An increasingly heavier and older workforce may be exacerbating the problem of slip-induced falls in the workplace. The purpose of this study was to examine the effects of obesity and age on slip severity and fall outcome following an unexpected slip. Four groups of participants (young obese, young non-obese, older obese, older non-obese) were exposed to an unexpected slip perturbation. Slip severity (slip distance, slip duration, average slip velocity and peak slip velocity) and slip outcome (fall or recovery) were compared between groups. Obese individuals experienced 8.25% faster slips than non-obese individuals in terms of average slip velocity (p=0.022). Obesity did not affect slip distance, slip duration or peak slip velocity. Obese individuals also experienced more falls; 33.3% of obese individuals fell compared to 8.6% of non-obese (p=0.005). Obese individuals were 8.24 times more likely to experience a fall than non-obese individuals, when adjusting for age, gender and gait speed. No age effects were found for slip severity or slip outcome. This study revealed that obese participants experienced faster slips and more falls than their non-obese counterparts. These results, along with epidemiological data reporting higher fall rates among the obese, indicate that obesity may be a significant risk factor for experiencing slip-induced fall. / Master of Science

The purpose of this study is to identify the pivotal factors contributing to programmatic success of arts programs for people, age sixty-five and older, in the United States. This study examines select programs within five arts disciplines: Elders Share the Arts (theatre), Museum One (visual art), Liz Lerman Dance Exchange (dance), New Horizons Music (music), and Arts for the Aging (writing/literature). The selected programs serve a heterogeneous population of older adults and exist independently of larger, non-arts institutions, such as hospitals, nursing homes, or senior care facilities. Success factors were determined by three methods, including: (1) direct questioning of program staff members about what they believed made their programs successful, (2) observations of program delivery to determine success factors in action, and (3) research and review of literature. The conclusions of the aforementioned methods result in six universal factors among successful programming within arts programs. These common factors are: 1. Reminiscence regularly occurs among individual participants. Older adults who have the opportunity to reflect, without inhibition, on events from their past tend to experience more self-satisfaction, a reinforcement of their identity, and a ready connection with other adults. 2. Programs establish and maintain a safe, non-threatening environment. Allocating a small amount of time for everyone to acclimate to the new environment allows older adults to feel more at ease, encourages their participation, and increases their enjoyment. 3. Teaching artists are personally committed to the context in which they work and exhibit patience when engaging with older adults. Teaching artists find a balance between activities that are aesthetically enjoyable and educationally and socially rewarding. 4. Another organization or venue serves as a host for the program. This reciprocal relationship sustains the arts program and increases the vitality of the host organization by providing a wide range of programs. 5. The organization's leader is enthusiastic and mindful of both challenges and opportunities in the field. A single person in a highly-placed administrative position is identified as an essential driving force behind successful programs. 6. Teaching artists demonstrate loyalty by committing several years to the programs. The long-term retention of all teaching artists ensures consistent, reliable, and quality programs. / Master of Fine Arts

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