Obviously, the test dates the age of the used wood and not an object’s date of manufacture.Due to technical reasons, using a C-14 test for an object dating between the eighteenth and middle twentieth century (being the most relevant period for African art), remains problematic (partly to blame on the Industrial Revolution).Another study on London taxi drivers suggested that the hippocampus grows with increasing knowledge of the city but this, too, has been controversial. “The existence of adult hippocampal neurogenesis in humans is not arguable this time,” says Sandrine Thuret at King’s College London, who was not involved in the work.
But studies in rodents and monkeys have shown that in two regions new neurons continue to be created even in adulthood – the hippocampus, which is involved in learning and the formation of new memories, and the olfactory bulb, which processes smell.
However, there has been some controversy over whether the same is true for humans.
The study also provides the first model of the dynamics of the process, showing that the regeneration of neurons does not drop off with age as sharply as expected.
In mammals, most types of brain cell are created at or soon after birth and are never renewed.
Nuclear bomb tests carried out during the cold war have had an unexpected benefit.
A radioactive carbon isotope expelled by the blasts has been used to date the age of adult human brain cells, providing the first definitive evidence that we generate new brain cells throughout our lives.
But instead of the 10-fold decrease between young and middle-aged mice, the team found only a four-fold decrease in humans, he says.
But the newborn brain cells in humans do not appear to live long. Many studies in mice show that young neurons are necessary for forming new memories. Journal reference: Cell, DOI: 10.1016/20 Correction When this article was first published on 7 June 2013, it counted the estimated daily number of new neurons in only one of the brain’s two hippocampi.
Fifteen years ago a study found evidence for such neurogenesis in adults up to the age of 72 (Nature Medicine, doi.org/b7hjfz), but the research relied on a chemical called bromodeoxyuridine (Brd U) to label neurons.