The power of our brain to form new cells, connections, and memories is an ability often consigned to the youth. We’ve heard the numbers: Shortly after birth, our brain contains around 86 billion neurons, roughly a quarter as many cells as there are stars in the Milky Way.
But can the golden years also be a prime time of growth for new neurons? Yes, according to a recent study published in Cell Stem Cell. Healthy older adults can produce just as many new brain cells as younger people aged 14 years and older. This is in stark contrast to a study published last month that claims otherwise.
For the current study, researchers from Columbia University autopsied the flash-frozen brains of 28 healthy men and women aged 14 to 79 years. They specifically studied the dentate gyrus of the hippocampus – the so-called memory hub of the brain, although it’s likely involved in other tasks as well.
"We found that older people have similar ability to make thousands of hippocampal new neurons from progenitor cells as younger people do," lead author Maura Boldrini, associate professor of neurobiology, said in a statement. "We also found equivalent volumes of the hippocampus across ages.”
However, this ability does not seem to hold true for blood vessel growth, which decreases with age. They also found fewer protein markers that indicate the ability of the brain to form new connections and fewer progenitor cells, those with the ability to go on to become a specific target cell. The team suggests that diminished cognition in old age may therefore have more to do with these factors than brain cell formation (neurogenesis).
Neurogenesis is currently rife with debate. Last month in Nature, a team from UC San Francisco found that the hippocampus does not form new brain cells. A 2013 study found that around 700 neurons in the hippocampus are made each day in adult brains.
This latest study adds to the evidence that adults can indeed form new cells in the brain. So why the difference between this team’s results and last month’s? Boldrini suggests it may have to do with the preservation method of the brains.
The recent team immediately froze the donated brains and stored them at -80°C (-112°F). Last month’s study used samples from hospitals in China, Spain, and the US and were treated with different chemicals from each other.
“In Arturo’s paper, he used brain tissue fixed in different ways, and compared results between them, attributing the findings to aging," Boldrini told IFLScience.
Also, "long post-mortem interval between the time of death and when the tissue was taken can severely affect the quality of the proteins and results." The UCSF study also only had access to slices of the hippocampus, while her team had the entirety.
These differences do not delegitimize the previous team’s findings, but rather provides an impetus for further research.
Mercedes Paredes, co-author of the UCSF paper, told IFLScience: "While the new study by Boldrini et al. offers interesting evidence of declining blood vessel growth in the adult hippocampus, we dispute the interpretation of their cellular staining experiments as evidence of new neurons in the adult brain.
"In our own recent study we made similar observations to what Boldrini et al. report, but after performing extensive additional analysis of the shape and appearance of the cells in question, including electron microscopy and gene expression, we determined that these cells were not in fact young neurons or neural progenitors but different types of cells altogether."
Others say the recent findings are sound. It seems the battle of the brains continues to simmer.