Atmospheric nuclear weapons testing went out of style decades ago, but the radioactive isotopes produced by thousands of explosions are with us to this day. Mostly harmless, these byproducts exist in minute quantities in our bodies and are not thought of as influencing any physiologic processes.
Conveniently, though, a team of researchers led by scientists from Karolinska Institutet in Sweden used these same fallout byproducts to answer a long standing question of whether adult human brains grow fresh neurons as we age. Essentially, the team measured the concentration of nuclear test derived carbon-14 in the hippocampi of adult brain tissue samples. Much like sample testing that paleontologists use to estimate when found bones were formed, the new technique helps identify when neurons were grown inside the brain. What the researchers found, somewhat surprisingly for some, is that the brain does grow approximately 700 new neurons every day, “corresponding to an annual turnover of 1.75% of the neurons within the renewing fraction.” Moreover, they compared neurogenesis rates between middle aged humans and mice and showed that we grow fresh neurons at approximately the same rate as our rodent cousins.
Study in Cell: Dynamics of Hippocampal Neurogenesis in Adult Humans…
Karolinska Institutet: New neurons generated in the hippocampus of adult humans…
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