The ability to forget irrelevant information reduces demands on mechanisms that detect and resolve conflict between competing memories, finds a study in the July 2007 issue of Nature Neuroscience. Thus, some kinds of forgetting allow later memory retrieval to use less of the brain's resources, making it easier to retrieve the correct memory.
Retrieving a particular memory often requires the inhibition of other memories that are not relevant to the task. Previous work has found that a part of the brain called the prefrontal cortex is important for such inhibition. However, this process comes with a cost: the suppressed competing memories are often forgotten, with people unable to recall them when they later become relevant. Brice Kuhl and colleagues now find that the prefrontal cortex is less activated when subjects have forgotten other memories that are competitive with the memory they are trying to recall, suggesting that less cognitive control is required during memory retrieval.
The authors used functional magnetic resonance imaging (fMRI) to look at brain activity as subjects tried to remember previously learned word associations. Some words had multiple associated words, and subjects were cued to recall only a specific one. Prefrontal cortex activation was reduced in proportion to how much the competing word associations had been forgotten. Forgetting something can be a frustrating experience, but this work suggests that forgetting can also have benefits for the efficiency of neural processing.
Brice Kuhl (Stanford University, CA, USA)
Abstract available online.
(C) Nature Neuroscience press release.
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