To Evolution

Scientists find signs of new brain cells in adults as old as 79

    Abdulaziz Sobh
    By Abdulaziz Sobh

    Categories: Science


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    Do we continue to add new neurons to our brain circuit throughout our lives? Or does our neuron count remain fixed once we reach adulthood?The scientific debate continues.In a report published Thursday in Cell Stem Cell, scientists at Columbia University present new evidence that our brains continue to generate hundreds of new neurons per day, even after we reach 70 years, in a process known as neurogenesis.To reach this conclusion, the lead author, Dr. Maura Boldrini, a researcher in the department of psychiatry at Columbia University, and her colleagues analyzed the brains of 28 deceased people between 14 and 79 years old. Its objective was to determine if aging affects the production of neurons.Previous research has shown that neurogenesis slows down in aging mice and in non-human primates. Boldrini's group wanted to see if a similar pattern occurred in humans.In each brain sample, the researchers looked for evidence of neurons at various stages of development, including stem cells, intermediate progenitor cells that would eventually become neurons, immature neurons that had not fully developed and new neurons.The team only looked at the hippocampus, in part because it is one of the few brain areas that previous research has shown can produce new neurons until adulthood. This region is involved in emotional control and resilience, as well as inEmory said Boldrini.In all of their samples, the researchers found similar numbers of neuronal progenitor cells and immature neurons, regardless of age. This led them to conclude that the human brain continues to produce neurons even in old age.

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    However, the researchers discovered some differences in the brains of the young and the elderly.
    Specifically, they discovered that the development of new blood vessels in the brain progressively decreases as people get older. They also discovered that a protein associated with helping new neurons make connections in the brain decreased with age."We did not find fewer new neurons or fewer of the progenitors of new neurons, but we discovered that the new neurons could make fewer connections," Boldrini said.This could explain why some elderly people suffer memory loss or exhibit less emotional recovery, he said.These new findings were published a month after a team of UC San Francisco researchers reported in Nature that they had not been able to find any evidence of neurogenesis after adolescence in humans.In an e-mail statement, that group, which works in the development neuroscientific laboratory Arturo Alvarez-Buylla, said that although they found that the evidence from the new study on the decrease in blood vessel growth in the adult hippocampus was interesting, they were not convinced that Boldrini and his colleagues found conclusive evidence of adult neurogenesis."Based on the representative images they present, the cells they call new neurons in the adult hippocampus are very different in shape and appearance from what would be considered a young neuron in other species, or what we have observed in humans in young children " they wrote.They added that in their study, they not only analyzed the protein markers associated with different types of cells, as Boldrini and his team did but also made a careful analysis of the shape and structure of the cells using light and electron microscopes. ."This revealed that similarly labeled cells in our own adult brain samples proved to be neither young neurons nor neural progenitors, but nonneuronal glial cells that express similar molecular markers," they wrote.Boldrini notes that the two groups were working with very different samples.She and her team examined more than two dozen fast-frozen human brains, which were donated by the families of the deceased at the time of death. The brains were immediately frozen and stored at -121 degrees Fahrenheit, which prevents the tissue from degrading.The other research team received brain samples from hospitals in China, Spain, and the US. UU. And the brain tissue they examined had not been preserved in the same way. Boldrini said the chemicals that were used to repair the brain could have interfered with their ability to detect new neurons.He also noted that while both groups were looking for signs of neurogenesis in the hippocampal region of the brain, their group had access to the entire hippocampus, while the UCSF team observed fine cuts of tissue representing a small fraction of the brain."In science, the absence of evidence is not evidence of absence," he said. "If you can not find something, that does not mean it's not 100% there."