New observations of the growth process of brain cells show that nerves not only repair, but are formed equally well in the memory center in both young and old people, according to an article published in the journal Cell Stem Cell.
“We found that the same tens of thousands of new neurons can form in the hippocampus of older people as in the brain of young people. This is also supported by the fact that the volume of the memory center for old people and young people is approximately the same. On the other hand, blood vessels supply it with less blood, and neurons may form fewer connections,”said Maura Boldrini of Columbia University in New York (USA).
Until the 1960s, it was believed that new neurons did not appear in adult mammals, and their death was compensated by the redistribution of functions among the remaining ones. In 1962, Joseph Altman from the United States, in experiments on rats, showed for the first time that the process of neurogenesis in adult rodents was under way, and 30 years later, in 1998, Peter Ericsson's group discovered that new cells were also formed in the brain of adults.
Recent observations of the functioning of the brain in humans and other mammals show that some cells, for example the olfactory center, are renewed almost continuously, while in other regions, including the hippocampus (memory center), there are rather large colonies of stem cells that are supposedly involved in neurogenesis.
In February, neuroscientists from Zurich proved that this is indeed happening. They tagged several stem cells in the brains of mice with glowing proteins and tracked their growth. Observations have shown that stem cells are rapidly depleted and almost completely disappear by old age. This immediately caused controversy among scientists, since it contradicts many other observations.
Boldrini and her colleagues also understood this issue, for which they studied the structure of fragments of the hippocampus extracted from the brains of three dozen young and old people who died in car accidents and for other reasons not related to diseases of the nervous system. After marking all stem cells with chemical dyes, they counted them and tried to understand whether their reserves are really depleted by the time of old age, and if so, how this affects the rate of formation of new neurons.
As it turned out, the reserves of some types of stem cells were indeed depleted. This did not in any way affect the speed and frequency of the appearance of new neurons in the memory center - other types of nerve cell blanks are involved in their formation, the number of which does not decrease with age. All this suggests that neurons continue to form until death.
On the other hand, old age still does not pass without a trace for the brain - in the hippocampus of older people there are fewer capillaries and other blood vessels, and new cells are less likely to form connections with neighbors. Why this happens is still unclear, but Boldrini and her colleagues believe that this may be due to a decrease in the number of the most specialized neuron presets.
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