Klotho, APOEε4, cognitive ability, brain size, atrophy and survival : A study in the Aberdeen Birth Cohort of 1936

We thank the cohort participants who contributed to these studies. The study was supported by the University of Aberdeen Development Trust; the UK’s Biotechnology and Biological Sciences Research Council (BBSRC); the Wellcome Trust; the Chief Scientist Office (Scotland); and the Alzheimer’s Research Trust (now ARUK).Peer reviewedPostprin

The role of cognitive reserve in executive functioning and its relationship to cognitive decline and dementia

In this chapter, we explore how cognitive reserve is implicated in coping with the negative consequences of brain pathology and age-related cognitive decline. Individual differences in cognitive performance are based on different brain mechanisms (neural reserve and neural compensation), and reflect, among others, the effect of education, occupational attainment, leisure activities, and social involvement. These cognitive reserve proxies have been extensively associated with efficient executive functioning. We discuss and focus particularly on the compensation mechanisms related to the frontal lobe and its protective role, in maintaining cognitive performance in old age or even mitigating the clinical expression of dementia.info:eu-repo/semantics/publishedVersio

Neural reorganization and compensation in aging

According to prominent theories of aging, the brain may reorganize in order to compensate for neural deterioration, and prevent or offset cognitive decline. A frequent and striking finding in functional imaging studies is that older adults recruit additional regions relative to young adults performing the same task. This is often interpreted as evidence for functional reorganization, suggesting that as people age, different regions or networks may support the same cognitive functions. Associations between additional recruitment and better performance in older adults have led to the suggestion that the additional recruitment may contribute to preserved cognitive function in old age, and may explain some of the variation among individuals in preservation of function. However, many alternative explanations are possible, and recent findings and methodological developments have highlighted the need for more systematic approaches to determine whether reorganization occurs with age and whether it benefits performance. We re-evaluate current evidence for compensatory functional reorganization in the light of recent moves to address these challenges

Inter-individual Differences in fMRI Entropy Measurements in Old Age

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI linkWe investigated the association between individual differences in cognitive performance in old age and the approximate entropy (ApEn) measured from functional magnetic resonance imaging (fMRI) data acquired from 40 participants of the Aberdeen Birth Cohort 1936 (ABC1936), while undergoing a visual information processing task: inspection time (IT). Participants took a version of the Moray House Test (MHT) No. 12 at age 11, a valid measure of childhood intelligence. The same individuals completed a test of non-verbal reasoning (Raven’s Standard Progressive Matrices [RPM]) aged about 68 years. The IT, MHT and RPM scores were used as indicators of cognitive performance. Our results show that higher regional signal entropy is associated with better cognitive performance. This finding was independent of ability in childhood but not independent of current cognitive ability. ApEn is used for the first time to identify a potential source of individual differences in cognitive ability using fMRI data

The Role of Cognitive Reserve in Executive Functioning and Its Relationship to Cognitive Decline and Dementia

In this chapter, we explore how cognitive reserve is implicated in coping with the negative consequences of brain pathology and age-related cognitive decline. Individual differences in cognitive performance are based on different brain mechanisms (neural reserve and neural compensation), and reflect, among others, the effect of education, occupational attainment, leisure activities, and social involvement. These cognitive reserve proxies have been extensively associated with efficient executive functioning. We discuss and focus particularly on the compensation mechanisms related to the frontal lobe and its protective role, in maintaining cognitive performance in old age or even mitigating the clinical expression of dementia

Perception, Cognition and Hetrogeneity in Autism Spectrum Disorder

Theoretical models of cognition in Autism Spectrum Disorder (ASD) propose that hierarchical processing is atypical and that perception is characterised by a local information processing bias. Whilst these models have gained considerable support from experimental studies, changes in ASD diagnostic criteria and increases in prevalence figures are reflected in increased heterogeneity at both cognitive and clinical levels in this condition. The aim of this study was to investigate perception and cognition in adolescents with ASD and typical development (TD) in the context of cognitive heterogeneity. Chapter two provided a detailed account of the standardised memory and intelligence tests administered in the study and the results from these tests were described in chapter three. Group differences, with poorer performance in the ASD group was observed on tests measuring verbal working memory, attention/concentration, whilst this group score higher on the Matrices subtest from the WASI-II (Wechsler, 2011). Inspection of individual data on standardised memory and intelligence tests revealed considerably variable subtest scores within the ASD group, and this was most marked on subtests measuring auditory and visual attention, visual perception, and memory for complex language. Experimental studies using flanker tasks to assess visual and auditory attention were presented in chapter four. The results from these studies showed some reduction in accuracy and an increase in RTs although responses to congruent and incongruent manipulations did not differ across groups. Experiment three, described in chapter five directly tested local and global processing using a Navon paradigm that included congruent and incongruent distractor trials. The group difference was marked on this study and showed a significantly increased susceptibility to both local and global incongruent distractors in the ASD group. The ASD scores on the selective attention and local/global processing tasks showed considerable within group variability and correlations carried out on the experimental and background data revealed links between task performance, cognitive and memory skills. In chapter six, a test of visual averaging was administered and failed to reveal a significant difference between the ASD and TD groups. These results were consistent with previous findings showing preserved visual averaging in adults with ASD. The results from the standardised and experimental tasks were discussed in chapter seven and it was concluded that the cognitive profile in ASD cannot be explained within a single theoretical model. Limitations in the studies and potential routes to better understanding heterogeneity in ASD were discussed

Cognitive and brain function in adults with Type 1 diabetes mellitus : is there evidence of accelerated ageing?

The physical complications of Type 1 diabetes mellitus (T1DM) have been understood as an accelerated ageing process (Morley, 2008). Do people with T1DM also experience accelerated cognitive and brain ageing? Using findings from research of the normal cognitive and brain ageing process and conceptualized in theories of the functional brain changes in cognitive ageing, a combination of cognitive testing and functional magnetic resonance imaging (fMRI) techniques were used to evaluate evidence of accelerated cognitive and brain ageing in middle-aged adults with T1DM. The first part of this thesis comprises a cognitive study of 94 adults (≥ 45 years of age) with long duration (≥ 10 years) of T1DM. Participants completed cognitive assessment and questionnaires on general mood and feelings about living with diabetes. Findings highlighted the importance of microvascular disease (specifically retinopathy) as an independent predictor of cognitive function. The incidence and predictors of mild cognitive impairment (MCI) were then explored. Results indicate a higher percentage of the group met criteria for MCI than expected based on incidence rates in the general population, providing initial evidence of accelerated cognitive ageing. Psychological factors were explored next. The relationship between the measures of well-being, diabetes health, and cognitive function highlighted the need for attention to patient’s psychological well-being in diabetes care. Finally, a subgroup of 30 participants between the ages of 45 and 65 who differed on severity of retinopathy were selected to take part in an fMRI study. Blood oxygen level dependent (BOLD) activity was evaluated while participants were engaged in cognitive tasks and during rest. The findings provided evidence that the pattern of BOLD activation and functional connectivity for those with high severity of retinopathy are similar to patterns found in adults over the age of 65. In line with the theories of cognitive ageing, functional brain changes appear to maintain a level of cognitive function. Evidence of accelerated brain ageing in this primarily middle-aged group, emphasizes the importance of treatments and regimens to prevent or minimize microvascular complications.