Clearing the Contents of Working Memory: Mechanisms and Representations

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 DESCRIPTION (provided by applicant): The overall objective of the current project is to understand the neural mechanisms that allow us to remove information from our current thoughts. For the last half century, it has been known that we have a limited capacity to concurrently keep information in mind at one time, typically considered to be about 7 items. This capacity is often referred to as working memory. Surprisingly, what is not known, however, is how we remove information from working memory, so as to either allow other items in or to clear it entirely. Understanding how information is removed from working memory, and which brain systems allow one to do so, is important not only from the perspective of obtaining a better understanding of how the brain influences the way we think, but also because such an understanding has important implications for psychological disorders. Many psychological disorders are characterized by an inability to remove certain types of information from working memory. For example, individuals with obsessive-compulsive disorder have difficulty not thinking about what harm might befall them or others, and individuals with depression have difficulty not ruminating on negative ideas and feelings. One of the reasons that it has been so hard to understand how information is removed from working memory is the large challenge involved in determining what a person might be thinking of at a particular point in time, and/or knowing whether indeed thoughts have been cleared from working memory. The goal of this project is to leverage brain-imaging techniques to overcome this problem. Recent techniques drawn from computer science allow one to characterize the pattern of brain activity associated with particular items (e.g., apples, pears, grapes, melons) or particular categories of items (frui, tools, faces, buildings). The project will utilize such methods to verify, via a pattern of brain activity, on which occasions individuals have either cleared their mind of certain items, or replaced them with other thoughts (e.g., switched from thinking about an apple to thinking about a pear, switched from thinking about an apple to thinking about a hammer). Then, the study will test the hypothesis that a certain set of brain regions in the prefrontal cortex plays a central roe in successfully changing the nature of the information held in working memory. In addition, the proposed research will examine how these neural mechanisms vary depending on differences across individuals. In particular, the project is designed to gather information both on how much difficulty an individual reports in controlling his or her thoughts, and also on the topics and characteristics of an individual's everyday thoughts (e.g., they are usually about things that happened in the past, negative, vague in scope, etc.). It is predicted that individuals who have difficulty controlling their thoughts and who have vague and over general thoughts will have more difficulty removing information from working memory, and they will show less activity in brain regions that control such thoughts. If this hypothesis is confirmed, it could provide new avenues for therapeutic intervention for psychological disorders characterized by repetitive thought.