Dissertation/Thesis Abstract

Rule and item information in working memory
by Montojo, Caroline A., Ph.D., The Johns Hopkins University, 2012, 218; 3525137
Abstract (Summary)

Humans can successfully engage in flexible, goal-oriented behavior in order to perform complex daily tasks. In order to achieve this behavior, it is necessary to maintain information about goals and rules along with information from the surrounding environment. How do our brains switch elegantly and quickly from one relevant rule to another according to a change in circumstances? The ability to hold information in mind over a short period of time for future use is referred to as working memory (WM). This term typically refers to the maintenance of item information, such as locations or words. More recently, investigators have emphasized the importance of rules that establish relationships between those items and the pending response.

This dissertation presents a series of studies investigating how our brains are able to flexibly hold or change the relevant rules held in mind. A central question is whether rules are represented in WM by patterns of neural activity that are independent of the particular items to which the rule applies. Experiment I examines the neural systems recruited for updating the rule (operation) or item (number) held in WM. While both types of updating activate a common network, rules activate prefrontal cortex while numbers activate parietal cortex, suggesting that rules and items are maintained in WM but they are different types of information that are controlled independently. Experiment 2 queries whether the neural systems for rules or items are similar for encoding compared to maintenance periods. Results show that rules are represented differently than items during both encoding and maintenance, providing support that rules are processed in WM as a different type of information than individual items. Experiment 3 queries whether other types of rules, such as relational comparison rules, share a similar representation with arithmetic operation rules. While some regions are commonly activated by operation and comparison rules, differences exist depending on the specific type of rule information being remembered.

Together, these 3 experiments illustrate that the neural mechanisms for rules and items in WM are distributed and largely overlapping, yet dissociations exist for coding these different information types.

Indexing (document details)
Advisor: Desmond, John
Commitee:
School: The Johns Hopkins University
School Location: United States -- Maryland
Source: DAI-B 73/12(E), Dissertation Abstracts International
Source Type: DISSERTATION
Subjects: Neurosciences, Cognitive psychology
Keywords: Cognitive control, Domain specificity, Humans, Prefrontal cortex, Working memory, fMRI
Publication Number: 3525137
ISBN: 9781267572981
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