6 - Working Memory

Summary

Learning Objectives

• To identify the brain regions that are thought to store the contents of working memory.

• To describe how information is coded in early sensory regions during visual working memory.

• To list three shortcomings of the evidence or analysis techniques that have been used to associate working memory and the hippocampus.

• To compare and contrast the brain activity frequency bands associated with working memory and long-term memory.

• To understand what types of changes take place in the brain after extensive training on working memory tasks.

Working memory refers to actively holding information in mind during a relatively short period of time, typically seconds (see Chapter 1). Like most long-term memory paradigms, working memory paradigms consist of a study phase, a delay period, and a test phase. During working memory paradigms, information is actively kept in mind during the delay period. Working memory is an explicit process as its contents dominate conscious experience. Working memory has been associated with activity in the dorsolateral prefrontal cortex, the parietal cortex, and sensory processing regions. Thus, the regions associated with working memory are similar to those associated with long-term memory (see Chapter 3), with the notable absence of medial temporal lobe regions such as the hippocampus. Section 6.1 of this chapter details the brain regions that store the contents of working memory during the delay period. It has long been thought that the contents of working memory are stored in the dorsolateral prefrontal cortex, but more recent evidence indicates that storage also takes place in early sensory cortical regions such as V1. In section 6.2, the evidence is evaluated that claims to link working memory with the hippocampus. In section 6.3, brain activity associated with working memory that oscillates at particular frequencies is considered, which includes alpha activity and gamma activity. This also mirrors the findings of long-term memory (see Chapter 4), except for the lack of working memory theta activity. Finally, in section 6.4, changes in brain activity are highlighted that have been linked to training-related increases in working memory capacity. These findings suggest that extensive training (e.g., multiple times a week for many weeks) on working memory tasks can produce long-term improvements in behavioral performance, change the way the brain functions for a period well beyond the time of training, and perhaps even increase intelligence.