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Discrete Representations in Working Memory: Developmental, Neuropsychological, and Computational Investigations

If you mentally rearrange your office furniture to accommodate a bigger desk, you're using what's called working memory. This is what the brain employs whenever a task requires multiple steps with intermediate results that need to be kept in mind so that the task can be completed. You rely on working memory, for example, when you calculate a tip in a restaurant, or compare features of mid-size cars made by different companies, or read a newspaper article. The project "Discrete Representations in Working Memory: Developmental, Neuropsychological, and Computational Investigations" undertook to explore how people learn to use working memory to assist in complex behavior.

The project, supported by the National Science Foundation KDI initiative, was the collaborative effort of a team from the University of Colorado at Boulder: Principal Investigator Akira Miyake, Professor of Psychology; and co-PIs Yuko Munakata and Randall O'Reilly, both Associate Professors of Psychology, and Michael Mozer, Professor of Computer Science.

In working memory, information is maintained in an active state in order to direct what the brain is processing and can be updated when new information comes in. Dr. Miyake and his team hypothesized that to hold information in this accessible state, even in the face of delays and interference, working memory representations should be discrete—meaning a finite amount of information should be represented in the brain. The team welcomed the challenge of investigating this hypothesis. "We were all interested in these general topics," said Dr. Munakata, "and we all were coming at them from slightly different perspectives, so we were really excited about working across our different perspectives."

They studied the ways in which the unique demands placed on the working memory system shape how it learns and develops, and how this affects the use of working memory as a whole. They did this in part with behavioral studies on 3-year-old children, adults, and some adults with brain damage. The team found that, for some experiments, they couldn't replicate the results of previous studies that supported their hypothesis. This led them to explore other ways—both experimental and using computational models—to test their theories.

The team developed a new computer modeling framework, one that describes computation in the brain in terms of how information is transmitted along processing pathways. According to Dr. O'Reilly, "What I did was develop computational models that looked in more detail at the biological basis of how these discrete representations might work in the cerebral cortex. Mike Mozer was working on somewhat more abstract computational models that were in some ways easier to understand but less closely tied to the biology, and then I worked on models that were more closely tied to the biology and were more complex. So it was really a nice combination of multiple levels of analysis."

The work of Drs. Miyake, Munakata, O'Reilly, and Mozer has applications in a number of ways. First, the project contributes to the growing body of literature that attempts to understand how different regions of the brain are specialized for certain functions. "The hope is that people would build on our work," said Dr. Munakata. "I know that that's already happening."

Their research is also useful for the many aspects of human activity that rely on working memory, from military planning, to air traffic control, to economic forecasting, and even to scientific research. It may also contribute to knowledge of techniques for rehabilitating working memory that has been impaired by brain injury and methods for assisting the development of working memory in children. In addition, understanding the mechanism of human learning and development can lead to an ability to design more intelligent and adaptive computer systems.

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