New neurons generated in the hippocampus of adult humans
The hippocampus is a region in the brain crucial for the ability to learn and remember. In a new study, published in the journal Cell, researchers at Karolinska Institutet show that a large number of new neurons are generated in the hippocampus of adult humans – which has long been an issue of debate. To reach this conclusion, the researchers measured the amount of carbon-14 found in humans as a result of nuclear testing during the 50s and 60s.
This unique strategy, using carbon dating to reveal the production – or lack of production – of new neurons in the human brain, was developed by Professor Jonas Frisén and his research group at Karolinska Institutet some years ago. Their most recent findings add new and important knowledge on brain development and cognition in adult humans.
"It was thought for a long time that we are born with a certain number of neurons, and that it is impossible to get new neurons after birth," says Jonas Frisén. "For several years now, it has been assumed that there is in fact some production of new neurons in the adult human brain, but to what extent and relevance to brain function has been unclear. In this current study, we provide evidence that there is substantial neurogenesis in the human hippocampus throughout life, suggesting that the new neurons may contribute to human brain function."
In the Cell study the researchers show that more than one-third of the neurons in the hippocampus are regularly renewed trough out life. Each day, about 1,400 neurons are being born in the adult human brain, the rate declining slightly during aging.
The research was funded with grants from the Swedish Research Council, the Tobias Foundation, the Swedish Brain Fund (Hjärnfonden), the Swedish Foundation for Strategic Research (SSF), AFA Insurance, the European Research Council (ERC), and the Knut and Alice Wallenberg Foundation, amongst others.