This thesis contains two studies which examined the cognitive functioning of the aging brain. Specifically, age-related changes in processing speed and its remediation via cognitive training were studied. In study 1, younger adults (n = 34) and older adults (n = 39) were recruited to investigate the age-related differences in the relationships between processing speed and general cognitive status (GCS). Their performance in GCS (as measured by The Montreal Cognitive Assessment, Hong Kong Version), cognitive processing speed (as measured by Processing Speed Index, Wechsler Adult Intelligence Scale), cognitive inhibition (as measured by Stroop Color-Word Test), and divided attention (as measured by Color Trails Test) was examined. Current findings indicated that processing speed predicted GCS in older but not younger adults. In older adults, processing speed as a predictor accounted for an additional 13% of variance in GCS. This study further verified the relationship between processing speed and prefrontal abilities, including verbal fluency, cognitive inhibition and divided attention in aging. Findings revealed that despite the abovementioned prefrontal abilities were significantly correlated with processing speed, verbal fluency had remained the strongest predictor, accounting for 21% of variance in processing speed in older adults. Based on findings in study 1, it was anticipated that training cognitive skills including processing speed and prefrontal abilities in older adults would improve cognitive functioning in general. Therefore, in study 2, elderly people at risk of progressive cognitive decline (n = 70) were recruited to investigate the training effect of computerized cognitive training programs that aimed to improve cognitive processing speed, cognitive inhibition and divided attention. Findings indicated that cognitive processing speed and divided attention improved post-training. Results obtained from the two studies implied potential intervention through training cognitive processing speed in elderly people at risk of progressive cognitive decline. Future studies should focus on training specific effect and examining the optimal effect by modification of the training paradigms, particularly the design of the contents and level of difficulty. / published_or_final_version / Clinical Psychology / Doctoral / Doctor of Psychology

Diss. (sammanfattning) Stockholm : Karol. inst. / Härtill 5 uppsatser.

No description available.

Bibliography : leaves 190-209. / xii, 209 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Psychology, 1995

Thesis (Ph. D.)--Psychology, Georgia Institute of Technology, 2001. / unknown, Committee Member. Includes bibliographical references.

Intentions have a special status in such important cognitive operations as prospective memory, or remembering to execute actions in the future. Indeed, recent research has shown that future-oriented information (such as intentions) have a higher and more sustained level of activation in mind than do other forms of to-be-remembered information. Such enhanced activation increases the accessibility of intentions for future retrieval operations, a phenomenon known as the “intention superiority effect.” Thus far, all research on the intention superiority effect has used facilitation paradigms, in which attending selectively to relevant stimuli facilitates performance on tasks that benefit from the processing of that information. The current investigation examines whether the intention superiority effect is also observed in an interference paradigm, in which sources of influence are in opposition. No previous research has demonstrated that the intention superiority effect is robust across such paradigm characteristics. Therefore, the first objective of the present study is to use a Stroop task to test the intention superiority effect within an interference paradigm. Previous research on the intention superiority effect has been conducted largely with undergraduate university students. Little is known about whether this effect exists for cognitively vulnerable populations, such as older adults. Arguably, the absence of an intention superiority effect could account for lower performance in such related cognitive tasks as prospective memory. Therefore, the second objective of this research was to examine whether the intention superiority effect, as produced by an interference paradigm, exists also for older adults. In a series of four experiments, participants received a brief Stroop word list including critical words from a previously encoded intention. We predicted that there would be more interference with colour naming for words that belonged to an intention that participants intended to carry out versus an intention that they did not have to carry out (i.e., intention superiority effect). Results of the four experiments for both young and older adults revealed longer latencies for words belonging to an intention that they intended to carry out. These data are the first demonstration of an intention superiority effect in an interference paradigm as well as the first demonstration of this effect in an older adult age group. / Graduate

The basis for sex differences in cognitive ability remains poorly defined and controversial both scientifically and politically. One of the biological hypotheses on sex differences, of particular relevance to this thesis, concerns the role of gonadal steroids, specifically testosterone (T) and oestrogen, and their relationship to individual differences in the performance of specific cognitive tasks. In addition, the role that age-related changes in these hormones play in relation to generalised and pathological cognitive ageing in males is studied. It is important to determine whether decreases in T levels that occur with ageing in males are associated with age-related decreases in cognitive performance because T levels can potentially be modified. Males have consistently been found to outperform females on measures of visuo-spatial function; performance on the Vandenberg and Kuse Mental Rotation Test (MRT) shows the largest and most robust of sex differences. Gonadal steroids have both organisational and activational effects which contribute to both withinsex variability and between-sex differences in visuo-spatial cognition. As males age, endogenous plasma T levels decline gradually yet variably between individuals. Studies in older males show improvement in visuo-spatial cognition following T supplementation; however, it remains to be resolved whether decreases in endogenous T levels with ageing are associated with poorer MRT performance. Some recent studies in older males have reported positive correlations between measures of plasma T levels and cognitive functioning, including processing speed and executive function measures. These data are inconsistent, however, and important questions remain concerning, for example: the age at which the effect is strongest; whether there are different effects at different ages; whether there is an optimal level at which T levels affect particular abilities; and which abilities show the strongest association with endogenous plasma T levels. Increased intra-individual variability in performance on Choice Reaction Time (RT) tasks has recently been shown to be a strong predictor of cognitive functioning in university students. Methodological advances in the analyses of RT distributions has allowed for the calculation of robust estimates of intra-individual RT variability. The association between these estimates and cognitive performance in middle and older aged males, however, remains to be determined. Further, the association between endogenous plasma T levels and intra-individual RT variability in aged males is unknown. The thesis addresses these issues; firstly, through cross-sectional analyses of the associations between different measures of plasma T levels, learning and memory, processing speed, and executive function performance in a large population based sample of 1046 men aged between 35 and 81 years. Secondly, further cross-sectional analyses are reported from a subsequent study in a healthy sub-sample of 96 of these men on the associations between endogenous plasma T levels, MRT performance, constituent abilities related to MRT performance, and performance on composite measures of both processing speed and executive function. In a third study, these data are re-analysed in relation to intra-individual variability in RT performance. In light of the results of these studies, the role that age-related declines in plasma T levels play in relation to generalised age-related cognitive decline in males is discussed. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1330807 / Thesis (Ph.D.) -- University of Adelaide, School of Psychology and School of Medicine, 2008

Thesis (Ph.D.) -- University of Adelaide, School of Psychology and School of Medicine, Discipline of Medicine, 2008. / "Thesis submitted in fulfilment of the Degree of Doctor of Philosophy, January 2008" Includes author's previously published papers. Bibliography: leaves 123-157. Also available in print form.

Thesis (M.A.)--Cleveland State University, 2008. / Abstract. Title from PDF t.p. (viewed on July 7, 2008). Includes bibliographical references (p. 31-36). Available online via the OhioLINK ETD Center. Also available in print.

Thesis (Ph. D.)--University of North Texas, Dec., 2009. / Title from title page display. Includes bibliographical references.