Behavioral and Electrophysiological Measures of Forgetting in Working Memory

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DESCRIPTION (provided by applicant): This project investigates forgetting from working memory, the small amount of information that is immediately available to conscious awareness. In particular this project investigates how time and distraction of attention away from memory maintenance cause people to forget items held in working memory. Impairment in working memory function is present in normal aging and a large number of mental disorders including schizophrenia, depression, attention-hyperactivity disorder, and post-traumatic stress disorder. Understanding its function in healthy adults is essential to understanding why this impairment occurs. Working memory performance will be measured in this project through a task involving presentation of an array of several visual items composed of multiple features that must be remembered over a retention interval. This interval will vary in both total duration and the amount of distraction present. The goal of this set of studies is to determine whether these items are forgotten gradually, feature-by-feature, or all at once. Verbal rehearsal of these items will be prevented by using items that are difficult to label in the memory task. After the retention interval a multiple choice response will be given in which the incorrect responses will differ in the amount of incorrect information they contain. If items are remembered perfectly until they are forgotten entirely then all incorrect responses should have the same amount of incorrect information on average regardless of total retention interval duration or amount of distraction. If forgetting occurs gradually, as if the memory blurs as it is forgotten, then incorrect responses should increase in the amount of incorrect information they contain as the retention interval increases or the level of distraction increases. It is possible that length of retention interval and amount of distraction may cause forgetting to occur in differing manners. After establishing how time and distraction-based forgetting occurs a physiological measure of the amount of information in mind, the contralateral decay activity (CDA) event-related potential component, will be measured and related to forgetting. Understanding the nature of the CDA and how it relates to forgetting is important because it can potentially serve as a measure of forgetting even when task performance measures are unavailable or difficult to acquire, as is often the case in many states of severe mental dysfunction. It is unclear whether the CDA indexes the number of features held in memory, such as color, shape, and orientation, or the number of entire items maintained. If the CDA is observed to be smaller when incorrect responses contain more incorrect information then it indicates that the CDA tracks the remembered features of items. If the CDA is smaller only for incorrect responses relative to correct responses, we can conclude that the CDA tracks the number of items remembered.