Although the fact that we generate new brain cells throughout life is no longer disputed, their purpose has been the topic of much debate. Now, an international collaboration of researchers made a big leap forward in understanding what all these newborn neurons might actually do. Their study, published in the July 10, 2009, issue of the journal Science, illustrates how these young cells improve our ability to navigate our environment.

“We believe that new brain cells help us to distinguish between memories that are closely related in space,” says senior author Fred H. Gage, Ph.D., …

When the first clues emerged that adult human brains continually sprout new neurons, one of the central tenets of neuroscience—we are born with all the brain cells we’ll ever have—was about to be overturned. Although it is never easy to shift a paradigm, a decade later the question is no longer whether neurogenesis exists but rather what all these new cells are actually good for.

“Adding new neurons could be a very problematic process if they don’t integrate properly into the existing neural circuitry,” says Gage. “There must be a clear benefit to outweigh the potential risk”.

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But pattern separation might not be the only role that new neurons have in adult brain function: a computer model simulating the neuronal circuits in the dentate gyrus based on all available biological information suggested an additional function. “To our surprise, it turned out that newborn neurons actually form a link between individual elements of episodes occurring closely in time,” says Gage.

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