It’s an old debate among neuroscientists; does the brain stop making new cells at a certain age? Indeed, it is commonly believed that the brain slows the creation of new neurons at very early ages. However, little by little, and in a timid way, various studies have begun to suggest the opposite.
According to a new work published in the journal Cell, carried out by a group of North American researchers, healthy people around the age of 70 have as many neurons or young nerve cells in a part of the brain related to memory as do the teenagers and young adults.
Understanding how the brain changes throughout life is essential to focus treatments against diseases such as depression, stress and memory loss, but also to reformulate pedagogical theories and methods. “The exciting thing is that the neurons are there throughout life,” said Dr. Maura Boldrini of Columbia University in New York and the lead author of the new study. “It seems that humans are different from mice, where [the production of neurons] decreases with age really fast and this could mean that we need these neurons for our complex learning abilities and the cognitive-behavioral responses to emotions,” she explained.
To reach this conclusion, the researchers studied the hippocampus of brains taken from autopsies of 17 men and 11 women aged between 14 and 79. Unlike other similar work, Maura Boldrini, a psychiatrist at Columbia University and colleagues also had access to the entire hippocampus of the subjects, rather than just a few slices, which allowed the team to make more accurate estimates of the number of neurons.
As reported by Science News, “although the number of neural stem cells was a little lower in people 70 years of age than in people in their 20s, older brains still had thousands of these cells. The number of young neurons in intermediate to advanced stages of development was the same for people of all ages. ”
This does not mean that aging does not charge a price. The researchers did find less formation of new blood vessels and fewer protein markers that indicate neuroplasticity, or the brain’s ability to establish new connections between neurons.
Regarding the findings and the contrary evidence presented by other works, Jonas Frisén, a neuroscientist at the Karolinska Institute in Stockholm who did not participate in the new research explained that “the small differences in methodology, such as the way in which the brains are preserved or how the neurons are counted, can have a great impact on the results, which could explain the contradictory findings.” However, he warned that the new document is the most rigorous study so far.
Dr. Mercedes Paredes of the University of California, San Francisco, author of an article published this year and which suggests that adults do not develop new neurons, told The Guardian that she was not convinced: “For now, we do not think this new study challenges what we have concluded from our own recently published observations: if neurogenesis continues in the adult human hippocampus, it is an extremely rare phenomenon. It boils down to interpretation of equivocal cells which we took extra steps to characterise extensively and showed not to be new neurons as they first appeared.”