Until the 1960s it was believed that adult mammals do not recover neurons, and neuronal cell death is compensated for by the redistribution of functions among the rest. In 1962, in the U.S, Joseph Altman in his first experiments on rats showed that adult rodents have the process of neurogenesis. And 30 years later, in 1998, Peter Eriksson’s team found that new cells are formed in adults’ brain, as well.
However, until now, scientists did not have the data on how fast the new neurons are, and if this process can seriously affect memory and thinking abilities. Kirsty Spalding of the Karolinska Institute (Sweden) and her colleagues used an unusual method to detect newborn cells – they were looking for neurons with a large concentration of the radioactive isotope carbon-14.
This isotope is chemically no different from the “normal” carbon-12 and is absorbed by the body, but at the same time, it is extremely rare. However, from 1945 to 1963, when the country conducted nuclear tests on the ground, in the atmosphere and in the ocean, the natural environment has obtained a huge amount of carbon-14, which appeared in nuclear explosions and got into people’s body with food. Scientists have found a large number of DNA-built neurons with carbon-14 in the hippocampus (the brain area associated with emotions and memory) of the people tested. The fact proved taht these cells appeared after birth.
The researchers found that adults form up to 700 new neurons per day in the hippocampus, with the rate of brain cell renewal of 1.75% per year. Spalding and her colleagues note that these late neurons may have a significant effect on brain functioning.