The present study attempted to investigate whether a combined weight and endurance training program can elicit more favorable changes in body composition than either method of training alone. Body composition parameters (absolute fat and fat-free weight) were evaluated using circumference measurements, skinfolds and hydrostatic weighing. Cardiorespiratory fitness was evaluated via a modified Harvard step-test. All tests were administered before and after 10 weeks of training. Exercises were performed 3 days/week for 40 minutes/day. Male volunteers (n=21) were randomly assigned to one of three treatment groups (weight training only, endurance running only, combined weight training and endurance running).

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Biological brains are composed of neurons, interconnected by synapses to create large complex networks. Learning and memory occur, in large part, due to synaptic plasticity -- modifications in the efficacy of information transmission through these synaptic connections. Artificial neural networks model these with neural "units" which communicate through synaptic weights. Models of learning and memory propose synaptic plasticity rules that describe and predict the weight modifications. An equally important but under-evaluated question is the selection of \textit{which} synapses should be updated in response to a memory event. In this work, we attempt to separate the questions of synaptic plasticity from that of memory addressing. Chapter 1 provides an overview of the problem of memory addressing and a summary of the solutions that have been considered in computational neuroscience and artificial intelligence, as well as those that may exist in biology. Chapter 2 presents in detail a solution to memory addressing and synaptic plasticity in the context of familiarity detection, suggesting strong feedforward weights and anti-Hebbian plasticity as the respective mechanisms. Chapter 3 proposes a model of recall, with storage performed by addressing through local third factors and neo-Hebbian plasticity, and retrieval by content-based addressing. In Chapter 4, we consider the problem of concurrent memory consolidation and memorization. Both storage and retrieval are performed by content-based addressing, but the plasticity rule itself is implemented by gradient descent, modulated according to whether an item should be stored in a distributed manner or memorized verbatim. However, the classical method for computing gradients in recurrent neural networks, backpropagation through time, is generally considered unbiological. In Chapter 5 we suggest a more realistic implementation through an approximation of recurrent backpropagation. Taken together, these results propose a number of potential mechanisms for memory storage and retrieval, each of which separates the mechanism of synaptic updating -- plasticity -- from that of synapse selection -- addressing. Explicit studies of memory addressing may find applications not only in artificial intelligence but also in biology. In artificial networks, for example, selectively updating memories in large language models can help improve user privacy and security. In biological ones, understanding memory addressing can help with health outcomes and treating memory-based illnesses such as Alzheimers or PTSD.

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The effects of physiological arousal and panic expectancy on anxiety and agoraphobic avoidance were evaluated on thirty-six Ss diagnosed with panic disorder. It was hypothesized that there would be main effects of increased physiological arousal and increased panic expectancy on anxiety and avoidance, as well as an interaction of these two factors, in a behavioral avoidance test containing agoraphobic situations. Physiological arousal induced through hyperventilation raised anxiety immediately following induction, but did not affect anxiety or avoidance on the subsequent walk. Although panic expectancy did not change as a result of the manipulations, initial panic expectancy was the strongest predictor of anxiety on the walk, and the best predictor of general agoraphobia measured by the Chambless Mobility Inventory. Absence of reliable changes in panic expectancy and significant results are discussed in terms of possible pretest sensitization, nature of the sample and subject selection, floor and ceiling effects, experimental demand characteristics, a relatively weak expectancy manipulation, and statistical issues such as large pre-group differences and large within-group variability. This research does however support previous studies which have found a strong correlational relationship between panic expectancy and agoraphobia. / Ph. D.

This investigation assessed the effects of acute exercise on blood pressure (BP) during a person's day-to-day life. It was hypothesized that there would be a reduction of systolic BP (SBP) and diastolic BP (DBP) at 1, 3, 5, and 7 hours following exercise as compared to a control condition. Additionally, it was speculated that those subjects with a greater reactivity to the cold pressor task would show a larger reduction than all subjects in mean BP. A secondary hypothesis was that there would be an attenuation of cardiovascular reactivity (CVR) following exercise. Fifteen college aged students enrolled in health education courses at Virginia Tech wore an ambulatory blood pressure (ABP) monitor for 2 days. These days were scheduled to be as equivalent in demands and activities as possible. On the morning prior to monitoring they took part in either an exercise or a control condition. During the exercise session they cycled for 30 minutes at 10% of their V02max. On the control day, they read for 30 minutes. The order of these two conditions was counterbalanced across subjects. Subjects then wore the ABP monitor for 12 hours while engaging in their usual activities. It was programmed to take readings every 20 minutes. A self-monitoring diary was filled out immediately following each cuff inflation. No significant differences were found between exercise and control days in either mean SBP or mean DBP. A subset of subjects most reactive to the cold pressor test also failed to show a significant effect. An analysis of standard deviations of mean BP did not reveal significant differences in CVR between the treatment and the control day. The selfmonitoring data indicated no significant differences across days in mood, stress, perception of the environment, and position/activity. This study does not support the hypothesis that SBP and DBP are attenuated during a person's daily activities following acute exercise. A number of limitations, however, might have reduced the power of the analysis. Differing schedules and demands between testing days may have introduced random error. In addition, the subjects tested have a number of characteristics which possibly render them relatively unresponsive to the exercise intervention. Future research, in which these limitations are corrected, will be necessary to determine if exercise exerts an acute effect on mean BP in the natural environment in populations at greater cardiovascular risk. / Master of Science