Attentional Control Processing in Working Memory: Effects of Aging and Bilingualism
Sullivan, Margot Diane
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Selective 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.