The idea that "you can't get brain cells back" has become outdated, and we can thank nuclear bombs for contributing to a new breakthrough.
Nuclear bomb testing in the 1950s and 1960s gave scientists insight into how the brain creates new neurons, LiveScience reported.
During this period the U.S conducted many above-ground nuclear bomb tests. After the testing stopped because of the Limited Test Ban Treaty of 1963, there was still evidence in the atmosphere. Neutrons that had flown off the bombs were reacting with the nitrogen in the air, which created an increase of carbon 14, an isotope.
The carbon 14 combined with the oxygen in the atmosphere to create carbon dioxide. This got mixed up in the photosynthesis process.
When humans ate the plants, they also ingested the carbon 14, a substance that is also used when a cell divides. The cells integrate the substance into the DNA of the new cells that are created from the division.
Since carbon 14 decays, it allowed researchers to study exactly when a new cell was born. This allowed them to see when new cells appeared in the adult brain.
It was once believed that after the brain was fully developed no further changes happened within it, new research has disproved this idea.
Kirsty Spalding, a biologist at the Karolinska Institute in Sweden who has been working on the study has been testing the carbon 14 in hippocampus cells for over a decade with her team.
What they found was the human hippocampus does grow new neurons. About a third of the region experiences cell turnover. The hippocampus, specifically, forms about 700 new neurons every day. The number remains constant because as new neurons form, older ones also die.
"Neurogenesis gives a particular kind of plasticity to the brain, a cognitive flexibility," Spalding said.
Researchers searched other regions of the brain for cell turnover, but could not find any evidence of the phenomenon.
They still don't have an explanation for why neurogenesis occurs in the hippocampus. The turnover occurs in an area called the dentate gyrus, which is credited with forming new memories. One theory is that this helps humans adjust to unique situations.
Researchers now plan to see if there is any correlation between the cell turnover and conditions such as depression.
