Healthy older adults can generate just as many new brain cells as younger people, researchers have found for the first time.
There has been controversy over whether adult humans grow new neurons, and some research has previously suggested that the adult brain was hard-wired and that adults did not grow new neurons.
The new study, published in the journal Cell Stem Cell, counters that notion.
"We found that older people have similar ability to make thousands of hippocampal new neurons from progenitor cells as younger people do," Boldrini said.
"We also found equivalent volumes of the hippocampus (a brain structure used for emotion and cognition) across ages.
"Nevertheless, older individuals had less secularisation and maybe less ability of new neurons to make connections," said Boldrini.
The researchers autopsied hippocampi from 28 previously healthy individuals aged 14-79 who had died suddenly.
This is the first time researchers looked at newly formed neurons and the state of blood vessels within the entire human hippocampus soon after death.
In rodents and primates, the ability to generate new hippocampal cells declines with age.
Waning production of neurons and an overall shrinking of the dentate gyrus, part of the hippocampus thought to help form new episodic memories, was believed to occur in aging humans as well.
Researchers, including those from New York State Psychiatric Institute, found that even the oldest brains they studied produced new brain cells.
"We found similar numbers of intermediate neural progenitors and thousands of immature neurons," they said.
Older individuals form fewer new blood vessels within brain structures and possess a smaller pool of progenitor cells - descendants of stem cells that are more constrained in their capacity to differentiate and self-renew.
Boldrini noted that reduced cognitive-emotional resilience in old age may be caused by this smaller pool of neural stem cells, the decline in vascularisation, and reduced cell-to-cell connectivity within the hippocampus.