A new study challenges decades’ worth of scientific notions which presumed that the brains of adults are able to create new neurons every day. Researchers now believe that this process, called neurogenesis, stops by the age of 13.
A team led by University of California San Francisco’s Arturo Alvarez- Buylla collected brain tissue samples from a total of 59 donors over a 5-year span. The samples were obtained from the deceased or from epileptic patients who had undergone brain surgery. Some tissues belonged to fetuses while others were from seniors between 60 and 77 years of age.
Researchers then used fluorescent antibodies to highlight specific proteins in the brain cells at various stages of maturity. Once the process was complete, they searched for the presence of young or immature neurons in each sample via a specialized electron microscope.
According to the study, human brains have massive amounts of progenitor and neural stem cells in early childhood. For example, a newborn has around 1,618 immature neurons in every millimeter of brain tissues.
Researchers found the cells to remain stagnant, in that, they didn’t multiply and develop into a layer made of NSCs. Neurogenesis dropped dramatically by 23-fold from ages one to seven. Neuron production then came to a halt upon reaching adulthood.
Researchers said that the oldest brain tissue that still contained a few immature brain cells belonged to a 13-year-old donor. No brain cells of this type were found in a tissue sample taken from an 18-year-old.
While the results were accurate, Gerd Kempermann, co-author of the study and neuroscientist at the Technical University of Dresden in Germany, said that their findings may not be so conclusive. He admits to the possibility of new neurons being formed that remained undetected in the older donors’ samples because of the fluorescent antibodies’ limitations.
The findings were published in the International Journal of Science: Nature.
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