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See Inside October/November 2007

Forgetting to Remember

Forgetting is a vital brain function

Lucy? Jane? Melissa? The next time someone's name stays frustratingly on the tip of your tongue, don't feel bad—your brain is just doing its job. Forgetting not only helps the brain conserve energy, it also improves our short-term memory and recall of important details, according to two recent studies.

Stanford University scientists asked students to study 240 word pairs and then instructed them to memorize only a small subset of the list, requiring the students to selectively retain some pairs and mentally discard others. Then the researchers performed MRI scans on the participants while testing them to see how well they had learned all the pairs. Those who could most often summon the target pairs were also the worst at remembering the others, suggesting that they were better at unconsciously filtering out unwanted memories. In addition, these subjects' MRI scans showed reduced activity in the prefrontal cortex, an area associated with detecting and resolving memory conflicts.

“When we want to remember things that are relevant, we put in much less neural effort if we have forgotten the things that are irrelevant,” says psychologist Anthony Wagner, a co-author of the paper. The findings suggest that memory suppression helps to conserve energy and improve efficiency—and some research indicates that efficient brains think faster.

A second study reveals that working memory, a form of short-term memory that both passively stores and actively manipulates information, benefits from an inhibition of long-term memory. Researchers investigating mice used x-rays or genetic techniques to stop the formation of new neurons in the hippocampus, which is important for long-term memory. These mice performed maze-related working-memory tasks better than normal mice did, suggesting “that by impairing one form of memory, long-term memory, it is actually possible to improve another form,” says Gaël Malleret, a neuroscientist at Columbia University and co-author of the study. So if you accidentally call Lucy “Melissa,” take heart—your brain probably just chose to dump her name in favor of a more crucial fact, such as where you left your keys.

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