Thesis (Ph. D.)--University of Queensland, 2002. / Includes bibliographical references.

published_or_final_version / Anatomy / Doctoral / Doctor of Philosophy

published_or_final_version / Public Health / Master / Doctor of Medicine

published_or_final_version / Psychology / Master / Master of Philosophy

Previous research had demonstrated cognitive biases towards threatening stimuli in anxious individuals, such as in attention, interpretation and memory. The present study aimed to examine the differences in memory-related information processing between anxious and nonanxious children and the effectiveness of a Cognitive-Bias Modification (CBM) based positive training in altering these differences. The study adopted a directed forgetting paradigm, where children with anxiety disorders (N=12) and healthy controls (N=12) were asked to either forget or remember word lists comprised of words of negative or positive valence, and were later asked to recall and recognize target words. The CBM training was subsequently administered, in which subjects were trained to endorse positive interpretations to ambiguous situations, followed by a similar directed forgetting task for post-training assessment. Results revealed that the CBM training was effective in reducing the hypervigilance towards negative words in anxious children, as well as reducing recall of negative words in all subjects. Clinical implications and limitations of the study were discussed. / published_or_final_version / Clinical Psychology / Master / Master of Social Sciences

Background Music as a part of our daily life, it can make people feel pleasure, peaceful, or exciting. Children as the future generation in our society are expected to have optimal development and growth. During childhood, cognitive development plays an important role in construction of thought processing ability and it is associated with physical development and nervous system development. As we know music is considered to be the efflorescence of human thought, this project aims to evaluate the effect of music listening and training on children’s cognitive development, as well as investigate effect of different types of music such as calm music, aggressive music, familiar music and unfamiliar music on cognitive development. The systematic review will identify and appraise the evidence of studies that related to our research question. Methods All relevant studies published from 1990 to 2013 were searched and identified when conducting an electronic literature search. There were 338 papers found through the database including Pubmed, SAGE and Google Scholar with a combination of specific keywords. After considering the inclusion and exclusion criteria, ten studies were found related to research questions and adopted for this systematic review. Results The ten studies were from four countries and included a total number of 8,836 subjects aged 4 to 12 years old. Randomized controlled trials, quasi-experimental studies, longitudinal studies, cross-sectional study were used in this systematic review. The studies included short-term and long-term effect of music listening and training on children. Most of the studies assigned participants to one group that had exposure to music and another group that had no exposure to music. For music listening groups, their performance of cognitive test was better than the group without music listing. Calm and pleasant music was more positive than aggressive music. Familiar music also had more impact on children’s cognitive ability. For music training groups, the effect of music gave impact on children’s cognitive development positively. Children received music training had increased cognitive ability. Conclusions Overall, the effect of different music listening and music training had been evaluated. The impact of music will be more effective if music is enjoyed by the listener. However, due to the publications of articles were only in English, not all of the studies design of articles were randomized control trials and some studies had small sample size such as thirty to seventy in this systematic review, further research is needed. / published_or_final_version / Public Health / Master / Master of Public Health

Alzheimer’s disease and vascular dementia are the leading causes of cognitive disorders in the elderly worldwide. Increasing cases with overlaps in neuropathology between both disorders are becoming evident, giving rise to the concept of “mixed dementia”, which is characterized by cerebrovascular dysregulations along with tauopathies and β-amyloid (Aβ)-associated neurotoxicity. While the exact mechanisms leading to the exhibited vascular-neurodegenerative pathophysiology are still unclear, it is often found that ischemic-stroke contributes to amyloid pathogenesis, thus exacerbating cognitive impairment. Astrocytes, the most abundant cell type in the brain, appear to be important mediators in the central nervous system homeostasis and pathophysiology. This study proposes that upon ischemic stress, endothelin-1 (ET-1) overexpression in astrocytes leads to β-site APP cleaving enzyme 1 (BACE1) upregulation, hence contributing to enhanced amyloid pathology. ET-1 is a potent vasoconstrictor associated to Aβ pathogenesis in the brain, and BACE1 is the rate-limiting enzyme for Aβ synthesis. In order to assess astrocytic responses to ischemic stress, two previously modified astrocytic cell lines, mock-transfected control astrocytes (WT) and ET-1 overexpressing astrocytes (C6), were used. The exposures of WT and C6 cells to oxygen and glucose deprivation (OGD) – to mimic ischemic stress in vitro – evoked no abrupt differences between both cell lines. After OGD, astrocytes were characterized by cellular swelling, detachment from neighboring cells, increased cell death, decreased cell proliferation, and reduced BACE1 expressions during reperfusion. In addition, the attempt to modulate BACE1 protein levels, by blocking the receptor for advanced glycation end products, induced no significant differences. This study also investigated astrocytic ET-1 influences in the neuropathology of the transgenic mouse models APPGET-1 (amyloid precursor protein and astrocytic ET-1 overexpression) and GET-1 through a proteomics approach. The abnormal expressions of tropomyosin-3, transgelin-3, ATP synthase α chain, 3-hydroxyisobutyrate dehydrogenase, superoxide dismutase 1, glutathione S-transferase P1, and peroxiredoxin-6 in the mice hippocampi were identified. It is most likely that these proteins participate in cytoskeleton structural changes, energy metabolism impairment, and oxidant-antioxidant system imbalances that contribute to the observed increased brain atrophy displayed in these two animal models. In summary, this study has identified the possible participation of several proteins in the accelerated declination of cognitive functions exhibited by GET-1 and APPGET-1 mice through a proteomics approach. However, our in vitro results suggest that ET-1 did not play any pivotal role in C6 response to the hypoxic conditions evaluated. Furthermore, results showed no correlation between astrocytic ET-1 and BACE1. Further investigations examining alternative BACE1-independent pathways are required to elucidate the intricate relationship between ET-1 and Aβ in astrocytes. / published_or_final_version / Psychiatry / Master / Master of Philosophy

Introduction: Cognitive impairments occur frequently in stoke survivors, yet current conventional post-stroke care focuses mainly on motor function. Transcranial direct current stimulation (tDCS) and repetitive transcranial magnetic stimulation (rTMS) are noninvasive brain stimulation techniques (NIBS) that are used in neurological rehabilitation. Its efficacy is well-established in motor recovery post-stroke, but research on its effects on the associated cognitive decline after stroke is fairly new. The aim of this review is to evaluate recent studies and provide a summary on the effects of NIBS on post-stroke cognitive decline. Methods: PubMed and CINAHL were searched using the keywords: “cerebrovascular accident”, “stroke”, “NIBS” or “noninvasive brain stimulation”, “tDCS” or “transcranial direct current stimulation”, and “TMS” or “transcranial magnetic stimulation”. PEDro system was used to assess the quality of the studies that passed the inclusion and exclusion criteria. Results: The initial search returned 1081 citations, among which 12 were included in this review. The mean PEDro score of the studies was 7.5 out of 10. The trials had a total of 176 participants with stroke. Lesion site was heterogeneous. Six trials investigated tDCS, and the other 6 investigated rTMS. The main outcome measures were grouped into 3 domains: memory, visuospatial, and attention. Both tDCS and rTMS resulted in significant changes in the visuospatial domain in terms of improving spatial neglect. The results on memory and attention are mixed, but tDCS shows more consistent results. Conclusion: NIBS is a safe and low-cost treatment that can improve cognitive decline post-stroke. However, the evidence is still lacking due to the small number of trials and sample sizes. More studies need to be conducted in order to establish a proper guideline for usage. Long term effects also need to be investigated. / published_or_final_version / Public Health / Master / Master of Public Health

Context: Dementia impairs daily functional ability and independence through negatively affecting cognitive function. As the prevalence of dementia increases, the burden on healthcare facilities and families grows, pointing to the need for providing further options available for the management of dementia in the community context. Of these options, physical exercise interventions are easily modifiable and relatively simple to implement. The primary objective of this review is to investigate the effectiveness of exercise for improving cognitive function in elderly people with dementia living in the community. Methods: A systematic review of 2 databases (PubMed and EMBASE) was carried out for all studies investigating the effects on cognition of a physical exercise intervention among home-dwelling elderly patients with dementia. Data was extracted on baseline characteristics of study participants, type of exercise intervention, length of follow up, and changes in cognitive outcome measures. Results: Seven studies were included. Three provided statistically significant results that showed an association between exercise and cognition in community-dwelling dementia patients.!The remaining four studies could not establish an association. Conclusions: The effectiveness of exercise for improving cognition in community-dwelling people with dementia is unclear based on the conclusions of this review. Small sample size and methodological quality limited the results. Further well-designed studies are needed that investigate appropriate community-based exercise interventions for people with dementia. / published_or_final_version / Public Health / Master / Master of Public Health

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