Psychology (Functional Area: Developmental Science)
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Browsing Psychology (Functional Area: Developmental Science) by Subject "Aging"
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Item Open Access Attentional Control Processing in Working Memory: Effects of Aging and Bilingualism(2018-11-21) Sullivan, Margot Diane; Bialystok, Ellen BSelective attention is required for working memory and is theorized to underlie the process of selecting between two active languages in bilinguals. Studies of working memory performance and bilingualism have produced divergent results and neural investigations are still in the early stages. The purpose of the current series of studies using older and younger bilingual and monolingual adults was to examine working memory processing by manipulating attentional control demands and task domain. It was hypothesized that bilinguals in both age groups will outperform monolinguals when verbal demands are low and when attentional control demands are high. Study 1 included behavioural tasks that varied by domain and attentional control. Study 2 addressed these factors by examining the neural correlates of maintenance and updating using ERPs. A third analytic approach using partial least squares (PLS) analysis was performed on the recognition data from Study 2 to assess contrasting group patterns of amplitude and signal variability using multiscale entropy (MSE). Bilingual performance was poorer than monolingual when the task involved verbal production, but bilinguals outperformed monolinguals when the task involved nonverbal interference resolution. P3 amplitude was largely impacted by attentional demands and aging, whereas language group differences were limited. Extensive language and age group differences emerged once whole brain neural patterns were examined. Bilingual older adults displayed a neural signature similar to younger adults for both amplitude and MSE measures. Older adult monolinguals did not show these patterns and required additional frontal resources for the difficult spatial update condition. Younger bilinguals showed long-range, frontal-parietal MSE patterns for updating in working memory. These results are consistent with the interpretation of brain functional reorganization for bilingual working memory processing and may represent adaptations to a top-down attentional control mechanism.Item Open Access Bilingualism as a Proxy of Cognitive Reserve(2021-11-15) Berkes, Matthias Daniel; Bialystok, EllenPrevious studies have reported bilingualism to be a proxy of cognitive reserve (CR) based on evidence that bilinguals express dementia symptoms ~4 years later than monolinguals yet present with greater neuropathology at time of diagnosis when clinical levels are similar. This dissertation presents two studies that provide further evidence for the contribution of bilingualism to CR. The first study uses a novel brain health matching paradigm. Forty cognitively normal bilinguals with diffusion-weighted magnetic resonance images recruited from the community were matched with monolinguals drawn from a pool of 165 individuals in the Alzheimers Disease Neuroimaging Initiative (ADNI) database. White matter integrity was calculated for all participants using fractional anisotropy, axial diffusivity, and radial diffusivity scores. Propensity scores were obtained using white matter measures, sex, age, and education as predictive covariates, and then used in one-to-one matching between language groups, creating a matched sample of 32 participants per group. Matched monolinguals had poorer clinical diagnoses than that predicted by chance from a theoretical null distribution, and poorer cognitive performances than matched bilinguals as measured by scores on the MMSE. The findings support the interpretation that bilingualism acts as a proxy of CR such that monolinguals have poorer clinical and cognitive outcomes than bilinguals for similar levels of white matter integrity even before clinical symptoms appear. The second study examines the role of biomarkers and genetic factors associated with Alzheimer disease in a sample of 641 individuals from the ADNI database. Gradient boosted regression modelling was used to examine the influence of 10 predictive factors on clinical diagnosis in 3 different models. Weighted propensity scores were applied to analyses of white matter integrity and cognitive performance between clinical groups in two models and between language groups in one model. Analyses revealed a strong influence of biomarkers and genetic factors on clinical diagnosis in monolingual participants, but underrepresentation of bilingual participants in the sample limited interpretations of the findings between language groups. The results of the second study indicate that information about biomarkers and genetic factors improves analyses exploring the role of CR on dementia outcomes.Item Open Access Putting the Distributed Practice Effect into Context(2019-03-05) Weston, Christina; Wiseheart, Melody SunshineSpaced repetition leads to superior final memory relative to massed repetition, a phenomenon known as the distributed practice effect. However, when items are repeated in variable study contexts across learning opportunities (relative to a consistent study context), the advantage of distributed practice over massed practice is typically reduced. In this dissertation, the effect of study context on the distributed practice effect was investigated from a neural perspective (Study 1) and from a developmental perspective (Study 2). In Study 1, event-related potentials (ERPs) were recorded as participants learned stimuli repeated after massed or distributed lags on either a consistent or variable background. After a fixed retention interval, stimuli were presented for a third time and participants recognition memory was tested. Behavioural evidence of a Lag x Study Context interaction was mixed. The ERP data revealed a neural distinction between massed and distributed repetitions during the study phase in terms of the late positivity component (LPC); however, the LPC was not further defined by the study context manipulation. During the test phase, distributed, variably studied repetitions engendered the greatest neural familiarity response compared to all other repetition conditions. In Study 2, younger and older participants learned stimuli repeated after varying lags on either a consistent or variable background. The background scenes were either shared among all to-be-learned items (Experiment 2A) or unique to each to-be-learned item (Experiment 2B). After the study phase, participants free recall memory was tested. Although older adults had greater difficulty identifying whether a repeated items study context had changed throughout the study phase, as hypothesized, they still exhibited similar final recall performance to younger adults during the test phase. Comparing data from the two experiments, the results also revealed that variations to study context might actually enhance the distributed practice effect in certain learning situations. This enhancement effect, which warrants further investigation, might depend on the type of material being learned and/or the variety of contextual information available during study.Item Open Access Task Switching Over the Lifespan(2020-05-11) D'Souza, Annalise; Wiseheart, Melody SunshinePeople often switch from one goal to another, in response to changing environmental demands. Task switching affords flexibility, but at a price. A robust switch cost ensues, whereby individuals are slower and less accurate when switching between tasks than when repeating tasks. The current dissertation investigated the factors that contribute to a switch cost, using an exceptionally large sample of over 25,000 individuals (ages 10 to over 65) collected online. Switch costs are interpreted as the duration of psychological processes that are recruited to shift between tasks. In Study 1, shifting a task took 576 ms (or 108%) longer than performing a single task. Shifting tasks resulted in a 34% immediate decrease in productivity. An additional 74% long-term decrease in productivity occurred from maintaining readiness for a shift, and for using a cue to select a task, both of which occur even without an actual shift taking place. The results show that the seemingly simple switch cost involves multiple processes. Understanding these processes is crucial to interpret how flexibility varies with age. In Study 2A, task switching process developed until adulthood and then declined, similar to general cognitive ability. However, each process changed differently with age. Findings show that decline is not simply development in reverse: The rate of decline in mid to late adulthood was up to 20 times slower than the rapid development in adolescence; Middle-aged adults were slower than young adults, but as accurate; They maintained less advance readiness but used contextual cues as well as their younger counterparts. In Study 2B, the effects of age were replicated in an independent sample using identical methodology. These findings highlight the usefulness of web-based data collection, effect size estimation, and segmented regression techniques.