Thesis (M.S.W.)--University of Hong Kong, 1983.

This study explored the relationship between working memory (WM) deficits and reading difficulties using secondary data analysis on data collected from 63 English speaking students in two urban school divisions in Saskatchewan participating in a larger SSHRC funded study (Marche, McIntyre, Claypool, 2013). First, this study addressed whether the WM profiles of individuals with reading difficulties were different from those of individuals without reading difficulties. The results showed that individuals with reading difficulties scored lower than individuals with average reading ability on measures of verbal short-term memory (STM), verbal WM, and visuospatial WM. Second, this study looked at the differential effects of computer-based WM training on the WM profiles of children with and without reading difficulties. The results showed that after WM training, there was a difference between the visuospatial STM scores of individuals with and without difficulties, when reading ability was determined by the combination of a decoding and comprehension task. Furthermore, a difference was also noted between the visuospatial WM scores of individuals with and without word decoding difficulties, and the visuospatial STM, verbal WM, and visuospatial WM scores of individuals with and without reading comprehension difficulties. Additionally, the verbal STM scores of individuals with reading comprehension difficulties were marginally different than the scores of individuals without. No differences were found between individuals who did not participate in WM training. The limitations of the study, as well as the implications for practice and future research, are discussed.

Working memory refers to the ability to retain information for short periods of time to guide future behavior. This type of short-term memory has been shown to play an important role in mental disorders such as schizophrenia and therefore further investigations into the neural basis of this cognitive function may aid in the study of disease states where this cognitive function is defective. A likely neural correlate of working memory has been identified in the persistent neural activity observed during the memory retention intervals of various behavioral tasks. Computational and cellular physiology has suggested that this persistent activity depends on NMDA receptor activation. Indeed, pharmacological studies on both human and animal subjects have reported a significant decrease in working memory task performance following the administration of NMDA-antagonists such as ketamine. However, the task and experimental design of these previous studies have not been ideal, and have therefore only shown equivocal evidence that NMDA-antagonists impair working memory, especially its capacity. Here we aimed to determine the effect of low-dose ketamine injection (0.25-mg/kg and 0.50-mg/kg IM) on the performance of macaque monkeys on a visual sequential comparison task, a task whose performance has minimal influence from other cognitive functions besides working memory. All monkeys showed a detrimental effect of ketamine administration on visual working memory performance, either at higher ketamine doses or with high memory loads. There was also an effect on performance in sessions without a memory component, indicating that the effect of ketamine was no limited to working memory maintenance. Although the effect of ketamine on memory load varied per animal, this study provides solid evidence in support of the hypothesis that working memory maintenance is dependent on NMDA receptor integrity. / Thesis (Master, Neuroscience Studies) -- Queen's University, 2011-05-27 14:56:41.726

Working memory is the ability to store relevant information temporarily to guide future thought and behavior. It is a basic cognitive function instrumental to processes such as learning, reasoning, comprehension and mental arithmetic. Central to mental disorders, such as attention deficit hyperactivity disorder (ADHD), are impairments in cognition including working memory. It is essential to understand working memory, if we want to understand human cognition and mental disorders. A neural correlate of working memory has been identified as selective persistent activity during the retention intervals of tasks that probe working memory. The signal-to-noise ratio of persistent activity can be modulated by catecholamines, neuromodulators that are depleted in many mental disorders, including ADHD. Such modulations should be evident at the level of behavior, particularly as the demands imposed on working memory are increased. To test the contribution of catecholamines to working memory, we opted to administer methylphenidate to three female macaque monkeys. Methylphenidate is a dopamine and norepinephrine reuptake inhibitor that effectively increases their availability in the brain. By having monkeys perform a visual sequential comparison task, which allows the systematic manipulation of working memory load, we tested the hypothesis that increased catecholamine levels modulate task performance in a dose- and memory load-dependent way. Systematic administration of a wide range of doses of methylphenidate (0.1 – 9 mg/kg) did not affect performance on the visual sequential comparison task in either a dose- or memory load-dependent manner. Given these results, we further tested the effects of methylphenidate on overt attention in a visual search task. Again, we did not observe a dose-dependent effect on performance. Nevertheless, methylphenidate was found to generally increase the monkeys’ motivation. We suggest that the positive effect on motivation, elicited by an increased level of catecholamines, might have led to changes in performance observed in previous literature, but not to changes in the ability of retaining visual information per se. These findings question the previously suggested influence that catecholamines exert on cognition, and suggest that the role of catecholamines in working memory should be reevaluated. / Thesis (Master, Neuroscience Studies) -- Queen's University, 2012-05-30 14:04:54.891

Previous neurophysiological and behavioural studies have shown that attention can be guided by the contents of working memory (WM), and that such guidance can be involuntary even when it is detrimental to the task at hand. In three experiments, this thesis investigated whether the guidance of visual attention from WM could be generalized from a specific stimulus or a task to a category. Experiment 1 tested whether maintaining a set of stimuli of a specific category in WM would influence participants' deployment of visual attention to favour other stimuli that belonged to the same category. Experiment 2 further manipulated the interval between the onset of a critical prime (i.e., a stimulus in the same category as the stimuli held in WM) and the target to determine whether the results of Experiment 1 were associated with the lack of time for attention to be focused onto the critical prime. In both experiments, the stimuli held in WM never appeared in the prime display. In Experiment 3, the identity of the prime was manipulated so that it matched the stimuli held in WM on half of the trials. The results showed that when the stimuli held in WM never reappeared in the prime display (Experiments 1 and 2) there was no evidence that maintaining specific stimuli in WM biased the distribution of attention to other stimuli within the same category. However, when the stimuli held in WM could reappear in the prime display on some trials (Experiment 3), the participants whose reaction times were relatively fast showed evidence for category-based WM guidance of attention when the critical prime item was a new stimulus in the same category as the stimuli held in WM. In contrast, the participants whose reaction times were relatively slow showed a non-spatially specific cost when the critical prime was one of the WM items than when it was a new item in the same category. These results showed that category-based WM could guide the deployment of visual attention under certain conditions. It further suggests that the relationship between WM and attention is more complex than what is outlined by the biased competition theory and related theories of attention.

The increasing involvement of mothers in paid employment has brought attention to child care both as a critical social issue and as a pressing need for families. Nevertheless, child care in Canada continues to be framed as a private issue to be resolved by individual families. In the absence of policies and programs that ensure widespread access to affordable, high-quality care, women who combine motherhood with paid employment face considerable challenges in making decisions about child care. This study examines the processes by which women make child care decisions and sheds light on both how and why they make such decisions. The emphasis is on the meanings that women themselves give to motherhood, paid work, and child care and on how they resolve the competing interests that inevitably underlie work and family decisions. By drawing on women's accounts of their own lives, the research elucidates the multiple and interrelated factors that enter into women's decisions and thus offers insights into the reasoning behind complex patterns of decision making. In-depth interviews were conducted with 25 women who were intending to return to work or school following the birth of their first child. Women were interviewed at three points in time, encompassing a period from late pregnancy to several months after returning to work. The study furthers our understanding of the public and private dimensions of child care by revealing the dilemmas faced by women who frame their child care concerns in deeply moral terms, yet are called on to meet their child care needs within a public market oriented child care system. In particular, women's accounts of their experiences demonstrate the ways in which the intertwined and deeply privatised notions of 'dependent child' and 'good mother' underlie women's decisions about child care. Moreover, the research leaves no doubt that women's experiences of making child care decisions do not accord with the prevailing neo-classical economics version of rational and self-interested decision making. By examining women's decisions over time, the study illuminates the sequence of decision making about child care and adds to our understanding of what is entailed in looking for and deciding about child care. The study concludes with a discussion of implications of the findings for policy development and future research.

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Many argue that there is a trade off between profitability and liquidity. However, many studies have found that the profitability can increase with an efficient Working Capital Management. Correctly allocating cash flows to where and when it is needed increases liquidity and simultaneously increasing profitability. The purpose of this study is to develop the research on the relationship between Working Capital Management and profitability by investigating how it is affected by different company characteristics. A quantitative method was applied with philosophical stances in objectivism and positivism and deductive theory was used to approach the subject. From the theoretical framework, five hypotheses were established and statistically tested in order to answer our research question. The first hypothesis was formulated to confirm previous research, while the remaining two aimed at providing both a theoretical and practical contribution to existing knowledge. The thesis centers on the Cash Conversion Cycle, a metric of how fast a company turns purchased products into profit, with Gross Profit Margin as the measure of profitability. The data analyzed is financial information from 2012, collected from a secondary source, Business Retriever database. In order to fulfill the purpose, hypotheses were tested. The first centered in previous research of the subject, while two were introduced based on research of company characteristics. This was tested in a cross-sectional study on the Swedish wholesale industry, covering a sample of 1,485 companies. The companies were segmented by size and whether they were listed or not. By using correlation and regression analyses, the relationship between Working Capital Management and profitability is compared between the different company groups. The conclusion drawn from the study is that there is a positive relationship between the Cash Conversion Cycle and profitability, inconsistent with previous research. However, strong significant results indicated that smaller firms are returning a higher profit, regardless the level of Cash Conversion Cycle. No difference was found in the sensitivity to changes in Working Capital Management strategies. This was true also for non-listed firms, although they were performing worse than listed firms in accordance to the theory presented. The foremost conclusion from the analysis is the weak explanatory power of the Cash Conversion Cycle on Gross Profit Margin. A debate is therefore included, discussing the possibility of lurking variables influencing the results. Keywords: Working Capital Management, Cash Conversion Cycle, Profitability, size, public, private, trade credit, wholesale industry, Sweden

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