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Brain cells that multiply to help birds sing their best during breeding season are known to die back naturally later in the year, according to a new study. 

For the first time, researchers have documented the series of events that cues new neuron growth each spring. The study added that it all appears to start with a signal from the expiring cells the previous fall primes the brain to start producing stem cells. 

If scientists can further tap into the process and understand how those signals work, it might lead to ways to exploit these signals and encourage replacement of cells in human brains that have lost neurons naturally because of aging, severe depression or Alzheimer's disease, said Tracy Larson, a University of Washington doctoral student in biology, in the press release. 

Researchers added that the study was first to examine the brain's ability to replace cells that have been lost naturally. 

"Many neurodegenerative disorders are not injury-induced," the co-authors write, "so it is critical to determine if and how reactive neurogenesis occurs under non-injury-induced neurodegenerative conditions."

"Tracy really nailed this down by going in and blocking cell death at the end of the breeding season," said Eliot Brenowitz, UW professor of psychology and of biology, and co-author on the paper. "There are chemicals you can use to turn off the cell suicide pathway. When this was done, far fewer stem cells divided. You don't get that big uptick in new neurons being born. That's important because it shows there's something about the cells dying that turns on the replacement process."

The study was published in the Journal of Neuroscience.