The Role of Attentional Control in Working Memory: Effects of Cognitive Load, Aging, and Stroke

Abstract

Working memory is a limited capacity system that relies on attentional control mechanisms to filter out task irrelevant information for optimal performance (Broadbent, 1958). The aim of this dissertation was to investigate the interactions between the closely related constructs of working memory and attentional control (e.g., Awh et al., 2006) in healthy and pathological aging (i.e., stroke). In both of these populations, deficits of attentional control (i.e., the ability to filter distractors) are thought to be a major contributor to declines in working memory performance. This dissertation examined distractor interference (DI) effects on the performance of healthy young adults, healthy older adults, and stroke survivors on an increasingly difficult working memory task. It was predicted that: a) regardless of group membership, the presence of distractors would result in increased response times (RT) and error rates (ER) compared to conditions in which there were no distractors, b) regardless of group membership, as task difficulty increased DI would increase (i.e., further increases to RTs and ERs when comparing distractor present and distractor absent conditions), and c) younger adults would show the smallest DI effects, older adults would show greater DI effects than younger adults and stroke survivors would show the largest DI effects compared to older and younger adults. The results suggest that for relatively simple working memory tasks attentional control mechanisms may not be engaged, as all participants showed significant DI effects. In contrast, in the more difficult working memory tasks DI effects were smaller than in the simpler tasks. This suggests that there are optimal conditions under which attentional control mechanisms are available and are applied to minimize the impact of distractors. Moreover, age and stroke status did not appear to affect the ability to apply attentional control mechanisms. These results support the theory that some aspects of top-down attentional control may be preserved in healthy and pathological aging.