Mar. 16, 2001 BRUNSWICK/PISCATAWAY, N.J. – Contrary to long-held popular belief, our brains may not only produce new brain cells or neurons throughout life, but the newly generated neurons quickly become involved in the formation of new memories – a fact that may have positive implications for the recuperative powers of our own brains when damaged by stroke or other disease or trauma.
In a study published today in the March 15 issue of the journal Nature, Rutgers psychology professor Tracey J. Shors and Princeton psychology professor Elizabeth Gould found that newly generated neurons in the hippocampus area of animal brains help form new memories.
Despite what is generally believed, scientists in recent years have learned that the brains of vertebrate animals, a category ranging from amphibians to humans, continue to produce new neurons throughout life. What was not known was whether the newly generated cells are actively involved in memory formation.
To find out, Shors and Gould studied the thousands of neurons produced daily in the hippocampus area of rat brains, an area that controls a form of memory known as trace conditioning, in which the animal must learn to associate stimuli that are separated in time. The researchers discovered that when they reduced the production of new hippocampus cells via a drug inhibitor, the rats were no longer able to form certain types of new memories.
This occurred even though mature hippocampus neurons remained functionally intact. On the other hand, when the researchers stopped administering the drug inhibitor, thus restoring the hippocampus area's ability to generate new cells, the ability to acquire trace memories was also restored.
"It appears that the new neurons become involved in memory about a week to two weeks after they are generated and they are involved in memories normally handled by the hippocampus," says Shors.
The team also noted that the reduction of new hippocampal cells had no apparent effect on memory that depends on other parts of the brain.
Although the researchers studied only the hippocampus, their research implies that the brain's recuperative powers may be far greater than previously thought. "We've known for some time that the brain generates new cells throughout life," says Shors. "These results suggest that one of the functions of these new cells is related to the process of memory formation."
In an earlier study, the two researchers demonstrated the nostrum, "use it or lose it." In the earlier study of rat brains, they found that while most new brain cells die within weeks of their generation, putting them to work through hippocampal-related learning improved their survival rate.
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