In healthy brains there was a "slight decrease" in the amount of this neurogenesis with age.
Human beings keep making new brain cells throughout their lives, even into the 90s, a finding that may pave the way to treatments for Alzheimer's disease -- linked to loss in brain cells, according to a study.
Scientists had earlier thought that most of our neurons -- brain cells that send electrical signals -- are indeed in place by the time we are born.
The team at the University of Madrid looked at the brains of 58 deceased people who were aged between 43 and 97 and focussed on the hippocampus -- a part of the brain involved in memory and emotion -- lost in Alzheimer's patients.
They were able to spot immature or "new" neurons in the brains that they examined, the BBC reported.
In healthy brains there was a "slight decrease" in the amount of this neurogenesis with age.
"I believe we would be generating new neurons as long as we need to learn new things," researcher Maria Llorens-Martin was quoted as saying to BBC News.
"And that occurs during every single second of our life," she added.
However, the study, published in Nature Medicine, says in people at the beginning of Alzheimer's, the number of new neurons forming fell from 30,000 per millimetre to 20,000 per millimetre.
"That's a 30 per cent reduction in the very first stage of the disease," Llorens-Martin said.
"It's very surprising for us, it's even before the accumulation of amyloid beta (a hallmark of Alzheimer's) and probably before symptoms, it's very early."
Understanding why there is a decrease in neurogenesis could lead to new treatments in both Alzheimer's and normal ageing, Llorens-Martin said.
"While we start losing nerve cells in early adulthood, this research shows that we can continue to produce new ones even into our 90s," said Rosa Sancho, from the Alzheimer's Research UK.
"Alzheimer's radically accelerates the rate at which we lose nerve cells and this research provides convincing evidence that it also limits the creation of new nerve cells."
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