Nuclear bomb fallout offers timeline for measuring brain development

If you lived during the early Cold War, you got nuked. On the other hand, you may have grown new brain cells.

That’s the take-away of research in the journal Cell that calculated the growth of brain cells in adult brains by using an isotope of carbon that was picked up by humans from the fallout due to above-ground nuclear testing from the late 1940s to 1963.

Neuroscientists have shifted from an old view that you’ll never have more neurons than you had when your brain was a pup. Studies have suggested that adult brains generate new neurons, particularly in the hippocampus, an area crucial to learning and memory.


It’s been hard to tell how many neurons are generated and if they are viable cells, because humans are not fond of having their brains removed. So a lot of the research uses mice and other animals.

Enter dead people and the carbon-14 isotope. The latter is a “heavy” carbon variant produced in nuclear reactions, such as blowing up a nuclear device out in the Pacific Ocean, a practice that was banned by treaty in 1963. Since photosynthesis doesn’t discriminate among carbon atoms it uses, vegetables, fruit and everything that eats them carry a signature ratio of carbon isotopes from the early Cold War atmosphere.

So researchers at Sweden’s Karolinska Institute measured the carbon ratios in gray matter that doesn’t matter anymore: donated brains of dead people. They calculated that as many as 1,400 new neurons had been added to these hippocampuses every day during adulthood.

The results suggest that cognitive functions may get a boost throughout adulthood. In other words, there may be truth in the addage that old age and treachery beat youth and skill.