Scientists had known that other animals, such as rats and mice, make new brain cells throughout their lives and there had been indirect evidence that humans beings can, too.
Using magnetic resonance imaging, or MRI, scans and electron microscope images of tissue donated from the brains of people who died, Maurice Curtis of the University of Auckland in New Zealand and Peter Eriksson of Sahlgrenska Academy in Goteborg, Sweden, and colleagues found the elusive cells.
Just as in mice and rats, these cells are born in one part of the brain and then migrate to the olfactory bulb, where smells are processed. They mature into neurons on the way.
In animals, they said, brain damage prompts the birth of new cells. "Our study provides the foundation for this possibility in the adult human brain," they wrote in their report, published in the journal Science.
Humans have far more developed brains, so searching for these cells has been harder than it was in rodents.
In mice and rats it has been clear these cells are born in the forebrain and then migrate to the smell centre. There, they can help the animals learn and adapt to new smells.
Smell is less important for humans, but it is still important for sensing dangers from smoke, for instance, or rotten food.
And studies show that the loss of smell may be an early sign of brain-destroying illnesses such as Parkinson\’s, the researchers said – a hint that these cells may be important.
"This study is exciting because it reveals a group of brain cells in the adult human brain that are continuously regenerating," said Dr Mark Baxter of Britain\’s Oxford University.
"Animal studies have pointed to the existence of such groups of cells, but it has been difficult to determine whether they exist in the human brain as well," Baxter, who was not involved in the research, said in a statement.
"This opens another direction by which we may discover ways to repair human brains that are damaged from injury or diseases, and underscores the importance of animal research in guiding biomedical research in humans," Baxter said.
Another expert, Sebastian Brandner, head of the Division of Neuropathology at the Institute of Neurology at University College London, agreed.
"These findings are important for several reasons: Understanding stem cell biology is essential to study brain repair in neurodegenerative diseases such as Alzheimer\’s and it is even possible that stem cells are the source of some brain tumours," Brandner said in a statement.