Brain diseases such as Alzheimer's and Parkinson's could be cured with drugs in as little as five years' time, according to scientists.
A study published today proves for the first time that a region of the brain contains stem cells, which have the ability to act as a repair system for the body.
As diseases such as Alzheimer's speed up the process by which brain cells die, scientists say that drugs could be developed which would stimulate stem cells to replace them, reports the Daily Mail.
This would mean that the body could be 'tricked' into repairing itself - reversing the damage caused to cells by a degenerative disease.
Professor Peter Eriksson, a neurobiologist at Sweden's University of Gothenburg, said: 'I think this discovery will open up totally new avenues of treatments for Alzheimer's and Parkinson's.
'It may be possible to develop a drug to trick the brain into replacing cells. <b1>
'It could also help patients who have suffered a stroke, as well as people with Huntingdon's Disease and schizophrenia.'
He added that the drugs could be developed.
A spokesman for the Alzheimer's Society echoed his enthusiasm, saying: 'This study raises the potential to treat damaged tissues and repair brain damage from neurological conditions, such as Alzheimer's disease.
'For the first time, this study demonstrates that stem cells are routinely involved in replenishing nerve cells in at least one part of the adult human brain.
'This process raises exciting new questions for the treatment of Alzheimer's disease, such as whether stem cells could be stimulated into action when the brain has been injured.
'These findings are the first step to unlocking potentially exciting new treatments.'
The study, published in Science magazine, was also welcomed yesterday by British scientists.
Dr Mark Baxter, Wellcome Trust senior research fellow at Oxford University, said: 'This study is exciting because it reveals a group of brain cells in the adult human brain that are continuously regenerating.
'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.
'This opens another direction by which we may discover ways to repair human brains that are damaged from injury or diseases.'
Scientists used to believe that the brain stopped producing new cells after the teenage years, when the body stopped growing.
It had been known for some years that some other mammals retained the ability to generate certain nerve cells well into adulthood.
Evidence that the phenomenon occurred in humans has been elusive but scientists in New Zealand and Sweden have now demonstrated it for the first time.
They used brain scanners on corpses to pinpoint the path that new cells take as they emerge from the centre of the brain to the region linked to the sense of smell.
Professor Eriksson said: 'There has been a long controversy about whether this structure exists in the human brain.
'It has been shown in rats and mice that these stem cells are essential for repair mechanisms to take place after a stroke.'
One of the main features of diseases such as Alzheimer's is that brain cells begin to die more quickly.
The finding raises the possibility that scientists could isolate a chemical compound to prompt stem cells in the brain to produce more of these cells.
However, some scientists warned that progress in this direction could be slow.
Jim Cohen, professor of cellular neurobiology at King's College London, said: 'We could be decades down the line of using this to come up with therapeutic treatments.
'There are many unknowns. For example we know these stem cells are present in one part of the brain - but how easy would it be to replicate them in a different part?'
Another option scientists could look at would be to transplant healthy regenerating cells into the brain of an Alzheimer's or Parkinson's disease sufferer.