Alzheimer’s disease (AD) is a neurodegenerative disorder with no existing cure. Since cognitive control influences saccade behaviour, saccades provide a valuable tool when studying cognitive changes in healthy and pathological aging. This thesis aims to evaluate differences in predictive capacity and working memory between cognitively normal older adults (NC) and mild AD patients using customized saccade paradigms and a battery of neuropsychological tests. In the predictive paradigm, we hypothesize that AD participants would display a decreased level of prediction, predictive capacity and learning capacity. In the memory-guided paradigm, we hypothesize that AD participants would have a decreased ability to maintain fixation and capacity to retain information and reproduce it correctly. Overall, we found that in the predictive paradigm, NC displayed a greater degree of prediction than AD participants. However, both groups had an optimal level of prediction at intermediate inter-stimulus intervals (ISI) (750 and 1000 ms). As ISI increased, both groups, although more so in AD, elicited a greater proportion of SRTs below -200 ms and -400 ms. This may suggest that as ISI increased, participants switched from a predictive to an anticipatory/guessing strategy. At an ISI of 500 ms, NC’s learning capacity was greater than AD participants. Cognitive scores of neuropsychological tests did not correlate with learning capacity in NC. However, learning capacity in AD participants was positively correlated with working memory capacity and attentional control. The memory-guided paradigm revealed AD participants completed less viable trials, less correct trials, and had more combined directional and timing errors than NC. Cognitive correlations showed that NC’s working memory capacity positively correlated with the frequency of correct trials, whilst negatively correlating with saccade errors. Since AD participants completed 10% of viable trials correctly, the task may have been too difficult for AD participants to comprehend, rendering correlations invalid. These findings suggest that although the predictive paradigm does not solely assess for prediction, it may provide a measure to cognitively differentiate NC from AD patients, and detect AD severity. Since the memory-guided paradigm may be too difficult for AD participants, it may provide a better indicator of cognitive changes associated with healthy aging. / Thesis (Master, Neuroscience Studies) -- Queen's University, 2013-05-21 18:54:19.492

The experiments in this thesis investigated the mechanisms controlling input and output gating of working memory. In chapter 3, accuracy and reaction time data from a precision/capacity working memory task with prospective and retrospective cues were analysed. The results suggest that retrocues boost performance by facilitating output gating from working memory. In chapter 4, the role of perceptual cortex in mediating the cue benefits in this task was investigated with magnetoencephalography (MEG). The pattern of alpha (8-12Hz) power in visual cortex was modulated by cue direction following both precues and retrocues, but whilst this modulation was sustained following a precue (until presentation of the memory array) it was transient following a retrocue, suggesting that a memory representation was briefly retrieved or refreshed, but that there was not a sustained biasing of top-down input to visual cortex following retrocues. This argues against the standard model of working memory as sustained attention to internal representations, and in favour of a more dynamic view in which perceptual cortex is recruited transiently, and otherwise freed up for on-going processing. In chapter 5, the role of frontal networks in precueing and retrocueing was investigated. An fMRI meta-analysis identified control networks involved in preparatory and mnemonic selection: whilst the fronto-parietal network is recruited in both cases, the cingulo-opercular network is recruited only by retrocues. This spatial pattern was replicated with a source-space ROI analysis of MEG induced-responses. These data also characterised the time-course of control network activation shedding light on their functional roles. The fronto-parietal network was activated immediately following both precues and retrocues, consistent with a direct role in top-down influence over perceptual cortex. By contrast, the cingulo-opercular network was activated following retrocues only after the perceptual refreshing event was complete, suggesting a downstream role, perhaps in selecting representations to guide action. Chapter 6 investigated the role of reward associations in controlling access to working memory, testing behavioural predictions of two theories implicating the dopamine system and basal ganglia in control of working memory. The results supported a temporal gating account in which encountering reward associated items triggers a brief (<300ms) window in which there is a boost of encoding for WM. Chapter 7 discusses the implications of the current work and suggests some future directions.

To determine if learned helplessness treatment debilitates human working memory and fluid intelligence, 60 university students, classified as high or low self-monitors, were assigned to one of three treatments: intermittent (50%) controllable positive feedback, uncontrollable (yoked) negative feedback, and no treatment. Test tasks included backward digit and backward spatial span (representing working memory), matrices (representing fluid intelligence), vocabulary (representing crystallized intelligence), and forward digit and forward spatial span (representing immediate span of apprehension). Results generally were not significant and were discussed as possibly due to ineffective treatment procedure. Further research on this topic is needed.

Thesis advisor: Marina Vasilyeva / This research explored the nature of gender differences in math performance across development. It examined potential mechanisms underlying gender differences by testing a mediation model in which females' higher anxiety taxes their working memory resources leading to underperformance on a mathematics test. Further, this research examined stereotype threat effects on math performance by testing whether female students presented with a scenario activating the stereotype would perform worse than females not exposed to the stereotype. Participants in Study 1 were 71 fourth, 107 eighth, and 147 twelfth grade students from high performing school districts. Students completed anxiety measures and a challenging mathematics test either in the stereotype threat condition or the no-threat condition. Results showed that there were consistent gender differences in math performance across all three grade levels; however, stereotype threat did not impact girls' math performance. Importantly, the relation between gender and math performance at the eighth and twelfth grade levels was mediated by the worry component of anxiety. This finding suggests that girls' heightened worry can explain their underperformance on a math test. In Study 2, the mediating relation observed in Study 1 was further explored by testing whether working memory mediated the relation between worry and math performance. Participants were 90 college students who were assigned to either the stereotype threat or no-threat condition. Students completed anxiety measures, two working memory tasks (verbal and visual), and a challenging math test. Again, findings showed a significant gender difference in math performance but no stereotype threat effects. Further, there was a mediating chain from gender to the worry component of anxiety to visual working memory to math performance. The results suggest that females' heightened worry taxes their working memory leading to gender differences in math performance. Both studies contribute to our understanding of affective and cognitive factors underlying gender differences in math performance. The findings of this research are discussed in terms of their implications for interventions and the future of women's participation in STEM careers. / Thesis (PhD) — Boston College, 2011. / Submitted to: Boston College. Lynch School of Education. / Discipline: Counseling, Developmental, and Educational Psychology.

Abstract South Africa has one of the largest population of adults living with HIV. About 30 to 60% of people living with HIV have been found to have HAND which can affect treatment with HAART which requires 95% compliance rate in order to be effective. Interventions that seek to alleviate the cognitive deterioration that is associated with HIV can include Internet based rehabilitation programmes. However, internet based interventions are plagued by poor adherence and attrition rates. The aim of the study was to describe the challenges and facilitating factors in the process of implementing the CogMed™ Working Memory Training Programme at a public HIV clinic for adults living with HIV. The study used a qualitative method with an ethnographic approach. Data was collected through CogMed™ administrator console, observations, interactions with gatekeepers, interactions and interviews with participants and interviews healthcare workers. The factors involved in the implementation process were categorised into the four “Stages of Use”. In the Recruitment/Consideration Stage perception of need, identifying and defining an ideal user were the main themes. Factors affecting the Initiation of Use Stage were sense of obligation, time to commit and access to suitable training environment. Utilisation of Service was influenced by ease of drop out, ease of use, perceived cost versus the perceived benefits of participating. Predisposing, enabling, and needs factors that affected adherence and participation were explored. Finally the Outcomes Stage covered the experiences and perceptions of using the rehabilitation tool. Limitations of the study were also discussed. Keywords: CogMed, Working Memory, HIV, HAND, Internet based interventions, Stages of Use

Introdução: Alterações no neurodesenvolvimento podem estar associadas à subnutrição. As consequências da subnutrição dependerão da idade da criança, do tipo, duração e grau da subnutrição. As possíveis alterações ocasionadas pela subnutrição são variáveis, porém, dentre essas alterações, a linguagem que é considerada uma das atividades cognitivas humanas mais elaboradas, apresenta grandes riscos. Objetivo: Caracterizar e analisar a linguagem oral e processamento fonológico de crianças que foram diagnosticadas com subnutrição em idade precoce adotando como referencial o desempenho de crianças na mesma faixa etária com bom e mau desempenho de linguagem receptiva e expressiva nas diferentes tarefas de memória de trabalho, consciência fonológica, fonologia e vocabulário. Método: Crianças com histórico de subnutrição em idade precoce (antes dos três anos de idade) e recuperadas nutricionalmente, foram avaliadas quanto à linguagem receptiva e expressiva, seu componente fonológico, vocabulário, consciência fonológica, memória de trabalho fonológica e memória visuo-espacial. Para possibilitar a análise desses componentes nessas crianças e se estabelecer parâmetro de comparação, foi realizada a avaliação de crianças eutróficas (sem histórico de subnutrição) na mesma faixa etária, pelos mesmos testes, e divididas em dois grupos (G1 crianças que apresentavam bom desempenho de linguagem e G2 - crianças que apresentavam mau desempenho de linguagem). O desempenho dos grupos foi comparado utilizando-se para inferência estatística dos resultados os testes t-student e Kruskal-Wallis. Para verificar possíveis associações entre os componentes avaliados foi utilizado o teste Exato de Fisher. Resultados: Nas crianças com histórico de subnutrição, observou-se que a criança que apresentou o quadro de subnutrição com menor idade, maior tempo de duração do diagnóstico e pior grau apresentou mau desempenho de linguagem e pior desempenho em todas as provas avaliadas no estudo quando comparada aos dois grupos de crianças eutróficas. Esse resultado sugere que essas variáveis (idade, duração e tipo) da subnutrição podem ser determinantes para os efeitos sobre a linguagem e processamento fonológico. As demais crianças que apresentaram variações na idade, duração e tipo de subnutrição assemelharam-se em algumas provas ao grupo G1 e em outras com o G2. Esse resultado reforça a suposição de que essas variáveis levam a diferentes prejuízos em linguagem e/ou processamento fonológico. Em relação à comparação de desempenho entre G1 e G2, os grupos apresentaram diferença significativa nas provas de memória de trabalho, tanto a fonológica quanto a visuo-espacial, não houve diferença para consciência fonológica. Os resultados não apontaram a existência de associação entre desempenho de linguagem, alteração fonológica e de vocabulário. Conclusões: Este estudo sugere que crianças que tiveram subnutrição no período crítico do desenvolvimento cerebral, mesmo após recuperação nutricional, apresentaram alterações cognitivas duradouras e importantes. / Introduction: Changes in the neurodevelopmental process may be related to undernutrition condition. The consequences of undernutrition appear to be dependent of childrens age, type, duration and degree of undernutrition. Undernutrition related alterations are diversified and the language that is considered to be one of the most relevant human cognitive skills may represent important risks. Objective: The aim of this study was to characterize and analyze the oral language and phonological processing of children diagnosed with undernutrition at early age using as standard of comparison the childrens performance in the same range age. Methods: Children presenting undernutrition at early age (diagnosed before reaching 3 years of age) with nutritional recovery were enrolled in this study and assessed for receptive and emissive language, phonology, vocabulary, phonological awareness, visuospatial and phonological working memories. Data obtained from these children were correlated with results collected from eutrophic children in the same range of age without undernutrition condition which were randomly divided in 2 groups (G1- children without language deficit and G2 children with language deficit) and submitted to the same tests. Data obtained from each group were averaged and compared using t-student and Kruskal-Wallis. Possible association between different language components was assessed by Fishers Exact tests. Results: In the children diagnosed with udernutrition, the infant with the highest level of disease (detected with the lower age and with the high long duration) shows significant language deficit and lower performance in all of the applied tests when compared with G1 and G2. This result suggests that age and duration and type of undernutrition may be determinant on the effects of language and phonological awareness. No significant differences were found between groups concerning phonological awareness. No association was found between language deficit and changes in phonology or vocabulary. Conclusions: Data obtained from this study suggest that children diagnosed with undernutrion during the critical period of brain development may present relevant and long-lasting cognitive alterations, even after nutritional recovering. In addition, data suggest that low performance may compromise working memories phonological and visuospatial.

Thesis advisor: Marina Vasilyeva / The ability to mentally store and manipulate information, termed working memory (WM), is essential to mathematical performance. Yet, little research has investigated the mechanisms through which WM capacity is related to mathematical performance in children. Furthermore, the extent to which children utilize specific WM resources when executing mathematical tasks is poorly understood. Addressing these gaps, this research investigated the nature of relations between WM and children's mathematical performance. Participants were 56 second and 32 fourth grade students from public and private elementary schools. Students completed tasks measuring their visuospatial-WM and verbal-WM capacities, the strength of their spatial and symbolic representations of numerical magnitude, and arithmetic performance. Arithmetic strategies were also assessed. In a dual-task condition, children's WM resources were experimentally manipulated: children completed mathematical tasks while retaining visuospatial and verbal stimuli in memory. Results showed that the relation between visuospatial-WM capacity and arithmetic accuracy was mediated by children's spatial numeric representations and the frequency of using a decomposition strategy in solving arithmetic problems. Conversely, the relation between verbal-WM and arithmetic accuracy was mediated by the frequency of using retrieval strategies in solving arithmetic problems. Additionally, the extent to which specific WM resources were involved in children's math performance varied by math task and children's skill level. Verbal-WM resources appeared to be minimally involved in children's spatial numerical representations, but highly involved in symbolic numerical representations and arithmetic calculations. On all math tasks, visuospatial-WM resources were involved to a greater extent among highly skilled children than low-skill children. The results suggest that WM capacity might improve spatial numerical representations and lead children to use memory-based arithmetic strategies more frequently, resulting in better arithmetic performance. Regardless of WM capacity, children who heavily use visuospatial-WM resources are more successful in executing mathematical tasks than children who rely on these resources minimally. These findings contribute to our understanding of how WM can facilitate children's mathematical performance. Implications for identifying specific challenges in children's mathematical learning are discussed. / Thesis (PhD) — Boston College, 2014. / Submitted to: Boston College. Lynch School of Education. / Discipline: Counseling, Developmental and Educational Psychology.

Fornecer dicas durante o período de manutenção de estímulos em tarefas de memória de trabalho melhora o desempenho dos participantes tanto para a acurácia quanto para o tempo de resposta (TR). Esse fenômeno é chamado de efeito de dicas retroativas. Nós realizamos três experimentos usando uma tarefa de reconhecimento de itens para testar a suposição de que o efeito das dicas retroativas é dependente de uma representação imagética disponível à inspeção consciente no momento da apresentação da dica. No Experimento 1, nós manipulamos o tamanho do conjunto (2 e 3 itens) a ser memorizado e inserimos uma tarefa de busca visual no intervalo de retenção para evitar a recitação visual dos estímulos. Nós aplicamos o método dos fatores aditivos de Sternberg para medir o tempo gasto pelos participantes para reativar os itens memorizados na forma de imagens mentais. O intercepto da função linear entre TR e tamanho do conjunto sofreu um incremento de 400 ms na presença da busca visual. No Experimento 2, nós inserimos 500 ms de tela em branco após a tarefa de busca visual e imediatamente antes do aparecimento da dica, para que os participantes usassem esse intervalo para reativar os itens na forma de imagens mentais. O efeito da dica retroativa ocorreu tanto para o TR quanto para o índice de discriminação (d). No Experimento 3, nós manipulamos a natureza da tarefa concorrente durante o intervalo de retenção: busca visual, monitoramento de tons e discriminação de cores. A busca visual foi a mais prejudicial ao desempenho dos participantes e ao efeito da dica retroativa, seguida pela discriminação de cores. A combinação de demanda atencional e necessidade de processamento visual presente na busca visual é especialmente prejudicial ao desempenho. Concluímos que o funcionamento das dicas retroativas é modulado por esses dois fatores, e não só por recursos atencionais centrais. Os resultados apoiam um modelo de memória de trabalho que considera o fenômeno da imaginação mental em sua arquitetura / Providing cues during the maintenance period of working memory tasks improves participants\' performance in terms of accuracy and response times (RT). This phenomenon is known as the retro-cue effect. We performed three experiments to test the assumption that the retro-cue effect relies on an imagetic representation of the stimuli, available to conscious inspection at the moment of the cue\'s onset. In Experiment 1, we manipulated the number of stimuli (set size 2 and 3) and inserted a visual search task during the retention interval to prevent visual rehearsal. We applied the Sternberg\'s additive factors method to measure the time participants spent to reactivate the items under the form of mental images. The intercept of the linear function between RT and set size increased 400 ms in the presence of the visual search. In Experiment 2, we added 500 ms of blank screen after the visual search task and immediately before the cue\'s onset, so that participants could use this interval to reactivate the items as mental images. The retro-cue effect occurred both for the RT and the discrimination index (d\'). In Experiment 3, we manipulated the type of the concurrent task during the retention interval: visual search, tone monitoring, and color discrimination. The visual search was the most deleterious task for the participants\' performance and for the retro-cue effect, followed by the color discrimination. The combination of attentional demand and visual processing in the visual search was particularly deleterious to performance. We concluded that the functioning of retro-cues is modulated by those two factors, and not only by central attentional resources. The results support a working memory model that considers the phenomenon of mental imagery in its architecture

Accurate memory for an object or event requires that multiple diverse features are bound together and retained as an integrated representation. There is overwhelming evidence that healthy ageing is accompanied by an associative deficit in that older adults struggle to remember relations between items above any deficit exhibited in remembering the items themselves. However, the effect of age on the ability to bind features within novel objects (for example, their colour and shape) and retain correct conjunctions over brief intervals is less clear. The relatively small body of work that exists on this topic to-date has suggested no additional working memory impairment for conjunctions of features beyond a general age-related impairment in the ability to temporarily retain features. This is in stark contrast to the feature binding deficit observed in the early stages of Alzheimer’s disease. Nevertheless, there have been reports of age-related feature binding deficits in working memory under specific circumstances. Thus a major focus of the present work was to assess these potential boundary conditions. The change detection paradigm was used throughout this work to examine age-differences in visual working memory. Despite the popularity of this task important issues regarding the way in which working memory is probed have been left unaddressed. Chapter 2 reports three experiments with younger adults comparing two methods of testing recognition memory for features or conjunctions. Contrary to an influential study in the field, it appears that processing multiple items at test does not differentially impact on participants’ ability to detect binding changes. Chapters 3, 4, and 5 report a series of experiments motivated by previous findings of specific age-related feature binding deficits. These experiments, improving on previous methodology where possible, demonstrate that increasing the amount of time for which items can be studied (Chapter 3) or mixing feature-conjunction changes in trial-blocks with more salient changes to individual features (Chapters 4 and 5) does not differentially impact on healthy older adults’ ability to detect binding changes. Rather, the argument is made that specific procedural aspects of previous work led to the appearance of deficits that do not generalise. Chapter 5 also addresses the suggestion that healthy ageing specifically affects the retention of item-location conjunctions. The existing evidence for this claim is reviewed, and found wanting, and new data are presented providing evidence against it. To follow-up on the absence of a deficit for simple feature conjunctions, Chapter 6 contrasts two theoretically distinct binding mechanisms: one for features intrinsic to an object and another for extrinsic, contextual features. Preliminary evidence is reported that the cost associated with retaining pairings of features is specifically pronounced for older adults when the features are extrinsic to each other. In an attempt to separate out the contribution of working memory capacity and lapses of attention to age-differences in overall task performance, Chapter 7 reports the results of an exploratory analysis using processing models developed in Chapter 2. Analysis of two data sets from Chapters 4 and 5 demonstrates that lapses of attention make an important contribution to differences in change detection performance. Chapter 8 returns to the issue of measurement in assessing the evidence for specific age-related deficits. Simulations demonstrate that the choice of outcome measure can greatly affect conclusions regarding age-group by condition interactions, suggesting that some previous findings of such interactions in the literature may have been more apparent than real. In closing the General Discussion relates the present work to current theory regarding feature binding in visual working memory and to the wider literature on binding deficits in healthy and pathological ageing.

Goal maintenance is the ability to keep task rules active in-mind so that they can guide behaviour. When this process fails, individuals are unable to use task rules appropriately, and consequently perform poorly on the given task. The rate of goal neglect has been shown to increase with the complexity of the information to be maintained, especially for those with low levels of fluid intelligence. The main aim of this thesis was to examine whether this effect arises from the limited capacity for task rules, the limited ability to cope with competition between task rules, or the limited ability to sustain maintenance of a rule over time both in younger and older adults. A second aim was to investigate whether fluid intelligence and processing speed contribute to performance when goal maintenance is taxed. In particular, the number of instructions presented at the start of the task (Experiments 1-4), the speed at which rules had to be used (Experiment 5), the infrequency with which a task-relevant goal was used relative to a task-irrelevant goal (Experiment 6), and the duration for which rules had to be maintained (Experiment 7) were manipulated. Finally, the importance of goal maintenance in a more real-world setting was examined by testing the relationship between goal neglect and academic performance in children (Experiments 8 and 9). Goal maintenance was not limited by the number of rules to be held in mind, but goal neglect did increase as the degree of competition between rules and the duration with which they were maintained increased. Fluid intelligence accounted for little of the variation in goal maintenance abilities, but processing speed played a moderating role in older adults. In terms of academic performance, goal maintenance in school-aged children significantly predicted mathematics abilities, but not language.