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- Hedner, Margareta, 1981-
(author)
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Olfactory Function : The Influence of Demographic, Cognitive, and Genetic Factors
- 2013
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Doctoral thesis (other academic/artistic)abstract
- Olfactory function is affected by demographic, cognitive, and genetic factors. In the present thesis, three empirical studies investigated individual differences in olfactory ability. Study I explored demographic and cognitive correlates in common olfactory tasks; odor detection, odor discrimination, and odor identification. The results indicated that old age influenced performance negatively in all tasks, and that semantic memory proficiency and executive functioning were related to odor discrimination and odor identification performance. No cognitive influence was observed for measurements of olfactory threshold. Using population-based data, Study II investigated a potential influence of the ApoE gene on olfactory identification after controlling for health status, semantic memory, and preclinical and clinical dementia. The main finding was that the ApoE- ɛ4 allele interacted with age, such that older ɛ4-carriers had an impaired odor identification performance relative to older non-carriers. Importantly, the negative ApoE- ɛ4 effect on olfactory proficiency was independent of clinical dementia conversion within five years. Study III investigated the effects of the BDNF val66met polymorphism on olfactory change over a five-year interval, in a community dwelling sample of young and old age cohorts. The results showed that age-related decline in olfactory identification was influenced by the BDNF val66met. In middle-aged subjects, no effect of BDNF val66met was observed although older val homozygote carriers showed a selectively larger olfactory decline than the older met carriers. Overall, results suggest that the relative influence of demographic and cognitive factors vary across different olfactory tasks and that two genes (ApoE and BDNF) impact age-related deficits in odor identification. Potential theoretical and practical implications of the findings are discussed as well as potential limitations of association studies in genomics research.
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| 2. |
- Holmgren, Sara, 1974-
(author)
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Effects of family configuration on cognitive functions and health across the adult life span
- 2007
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Doctoral thesis (other academic/artistic)abstract
- This thesis examines whether childhood family configuration influences performance on cognitive functions and health in adulthood and old age. All studies examined participants in the Betula Prospective Cohort Study aged 35 to 85 years (Nilsson et al., 1997). Study Ι established whether there are reliable effects of sibship size and birth order in a large sample of participants in adulthood and old age. The results showed that the effects previously demonstrated in children and adolescents (e.g., Belmont & Marolla, 1973; Mercy & Steelman, 1982) have a long-lasting effect and can be demonstrated in an adult sample. These studies concluded that intelligence and executive functioning decreased as the sibship size increased. Birth order, in contrast, had only influenced executive functions and working memory: earlier born siblings performed at a higher level than later born siblings. Study ΙΙ examined whether the effects of sibship size and birth order can be replicated and extended to episodic memory and whether the effects of family configuration are stable over a five-year interval. The results showed that early born siblings and siblings belonging to a smaller sibship size performed at a higher level and that these effects on both recall and recognition were stable over a five-year interval. Study ΙΙΙ explored whether childhood family configuration influences chronic adult diseases (myocardial infarction and circulatory disorders, stroke, and hypertension). The overall results showed that being born in a large sibship is a risk factor for stroke, myocardial infarction /circulatory disorders, and hypertension in old age. The results also suggest that being born early in a sibship is a predictor of stroke.
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| 3. |
- Kubik, Veit, 1981-
(author)
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Effects of Testing and Enactment on Memory
- 2014
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Doctoral thesis (other academic/artistic)abstract
- Learning occurs not only when we encode information but also when we test our memory for this information at a later time. In three empirical studies, I investigated the individual and combined effects of interleaved testing (via repeated rounds of study and test practice) and encoding (via motor enactment) during learning on later cued-recall performance for action phrases. Such materials (e.g., “water the flowers”) contain a verb and a noun and approximate everyday memory that typically revolves around past and future actions. Study I demonstrated that both interleaved testing (vs. study only) and enactment (vs. verbal encoding) individually reduced the forgetting rate over a period of 1 week, but these effects were nonadditive. That is, the direct testing effect on the forgetting rate occurred for verbal, but not for enactive encoding; enactment reduced the forgetting rate for the study-only condition, but not for the study–test condition. A possible explanation of these findings is that both study techniques sufficiently elicit verb–noun relational processing that cannot be increased further by combining them. In Studies II and III, I replicated these testing-effect results and investigated whether they varied as a function of recall type (i.e., noun-cued recall of verbs and verb-cued recall of nouns). For verbal encoding (Study II), the direct testing effect was of similar size for both noun- and verb-cued recall. For enactive encoding, the direct testing effect was lacking irrespective of recall type. In addition, interleaved tests enhanced subsequent re-encoding of action phrases, leading to an accelerated learning. This indirect testing effect was increased for the noun-cued recall of verbs—for both verbal and enactive encoding. A possible explanation is that because nouns are semantically more stable, in that the meaning of nouns changes less over time and across different contexts, they are more recognizable. Hence, associated information (e.g., about the recall status) may be more available to the learner during restudy that, in turn, can initiate more effective re-encoding. The two different testing benefits (i.e., direct and indirect) may, partly, engage different mechanisms, as they were influenced differentially by the manipulations of encoding type and recall type. The findings presented in the thesis provide new knowledge regarding the combined effects of strategies and materials that influence memory.
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| 4. |
- Moniri, Sadegheh, 1959-
(author)
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Bilingual memory : A lifespan approach
- 2006
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Doctoral thesis (other academic/artistic)abstract
- Bilingualism and its effect on individuals have been studied within different disciplines. Although the first psychological study of bilingualism was couducted by Cattell as early as 1887, only a few studies have exclusively investigated the effect of bilingualism on memory systems’ functioning. In the field of cognitive psychology of bilingualism, there is some evidence for the positive influence of bilingualism on children’s cognitive ability across various domains but there is little knowledge about the relationship between bilingualism and memory in a lifespan perspective. This thesis’s main aim was to investigate memory systems’ functioning and development in bilingual individuals. To this end, two studies were performed: a cross-sectional study of bilingual children (Study I) and a longitudinal study of young and older adults (Study II). The purpose of Studies I and II was to determine whether there are differences between monolinguals and bilinguals regarding various memory systems’ functioning. Study I compared monolingual and bilingual children’s performance on episodic and semantic memory, and Study II investigated performance on episodic and semantic memory in bilingual younger and older adults. Specifically, these studies aimed to examine a) which memory systems will be affected more as a function of language, and b) to what extent the differences would manifest themselves during a subject’s lifespan. The purpose of Study III was to explain the relation among word representations, lexical access and lexical selection in a bilingual word production paradigm. In this study, a model of bilingual production was developed to explain the results and clarify the role of automatic and controlled processes in using two languages. The results of Studies I and II showed a superiority of bilinguals over monolinguals as well as a variation of association between memory performance and bilingualism across different periods of adulthood. It appears that the lifelong experience of managing two languages enhances control processes, which in turn play an important role in enhancing memory performance. Using a “dual mechanism model”, Study III explains the efficiency of inhibitory processing when having two languages activated.
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| 5. |
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| 6. |
- Stenfors, Cecilia U. D., 1982-
(author)
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Subjective Cognitive Complaints in the Working Population : The Influence of Objective Cognitive Functioning and Working Conditions
- 2013
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Doctoral thesis (other academic/artistic)abstract
- Cognitive functioning is important for managing work and life in general. However, subjective cognitive complaints (SCC), involving self-perceived difficulties with concentration, memory, decision making, and clear thinking are common in the general and in the working population and can be coupled with both lowered well-being and work ability. The present thesis investigated the extent to which SCC among people in the work force can be explained by objective cognitive functioning (study I & II) and working conditions (study III), utilizing samples from the working population. The potential roles of other common psychological problems which often co-occur with SCC were also investigated in studies I-III.In Study I, high levels of SCC were associated with significantly poorer episodic memory performance during high executive demands and a trend was found towards poorer episodic memory, while not being associated with semantic memory. In Study II, high levels of SCC were associated with significantly poorer executive cognitive performance on all three executive cognitive tests used. Symptoms of depression, chronic stress and sleeping problems were found to play an important role in the relations between SCC and episodic memory during divided attention in study I and executive cognitive functioning in study II. In Study III, in all cross-sectional data analyses, high quantitative demands, information and communication technology (ICT) demands, underqualification in the work situation and inter-personal conflicts were positively associated with SCC, whereas social support, good resources at work and overqualification in the work situation were negatively associated with SCC. In all prospective data analyses, quantitative job demands, ICT demands and underqualification were positively associated with future SCC, including when adjusted for baseline cognitive complaints.The findings may guide prevention of and interventions for SCC among people in the work force.
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| 7. |
- Sternäng, Ola, 1961-
(author)
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Individual differences in the aging memory : Mediation accounts, moderators, and contextual factors
- 2010
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Doctoral thesis (other academic/artistic)abstract
- Within the field of cognitive aging, mediation accounts propose that age affects cognitive abilities through a mediator variable. Most of these mediation accounts are developed based on studies with cross-sectional designs. We had access to data from Betula, a longitudinal population-based multi-cohort project, and tested, in Study I, the well-known processing speed account (general age-related slowing of mental processing speed affects cognitive abilities negatively) (Salthouse, 1996). Interestingly, no support was found for the speed account. In Study II, a second mediation theory was tested, the common cause account (Lindenberger & Baltes, 1994). This notion suggests a link between sensory and cognitive abilities, where both abilities decline with age in a similar fashion because of a third factor, a common cause. Again, no support for a major account of cognitive decline was found. In Study III, interactions including vascular health and genetic status (APOE status) as potential interacting predictors of cognitive development were examined. A difference in the distribution of interaction effects on episodic and semantic memory development was found. Study IV, finally, consisted of a comparison of cognitive aging in two very different countries, Bangladesh (Poverty and Health in Ageing) and Sweden (Betula). The findings were surprising since chronological age, in Bangladesh, did not exert much effect on declarative memory in older people, in contrast to Betula and most other aging studies, predominantly performed in the Western world. Results from these four studies are discussed with respect to theoretical implications and methodological considerations. Recommendations for future research focus are made and implications for explanatory models of cognitive aging are elaborated on.
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| 8. |
- Söderlund, Göran, 1955-
(author)
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Noise improves cognitive performance in children with dysfunctional neurotransmission
- 2007
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Doctoral thesis (other academic/artistic)abstract
- Research on children with Attention Deficit Hyperactivity Disorder (ADHD) has shown that they are extremely sensitive to distraction from external stimuli that lead to poor cognitive performance. This thesis shows that cognitive performance can be improved if this external stimulus is smooth and continuous (e.g. auditory white noise). Control children attenuate their performance under such conditions. The first Study proposes the moderate brain arousal model (MBA). This neurocomputational model predicts selective improvement from noise in ADHD children. Noise through a phenomenon called stochastic resonance (SR), can be beneficial in dopamine deprived neural systems. The statistical phenomenon of SR explains how the signal-to-noise ratio can be improved by noise in neural systems where the passing a threshold is required. The second Study provides experimental support for the MBA-model by showing that ADHD children improve performance in a free recall task while exposed to auditive noise. Control children declines in the same condition. The third Study generalizes this finding among low achieving children, which it is argued have low dopamine levels. Noise exposure improves performance in low achievers, but inhibits performance in high achievers. The conclusion is that external auditory noise can restore low dopamine levels and thus improve cognitive performance. It is also proposed that dopamine levels modulate the SR effect; this means that low dopamine persons require more noise to obtain an SR effect. Both excessive and insufficient dopamine is detrimental for cognitive performance. The MBA model can be used to explain several shortcomings where changes in the dopamine system have been identified. The MBA model can also help create appropriate and adaptive environments, especially in schools, for persons with a deficient dopamine function, such as ADHD children.
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