New findings suggest ageing brains can potentially be rejuvenated, at least in mice, according to researchers.
Very early-stage experiments show that drugs can be developed to stop or even reverse mental decline.
The results were Presented at the 201
The United States and Canadian researchers took two new approaches to preventing the loss of memory and cognitive decline that can come with old age.
One team , from the University of California, Berkeley, showed MRI scans which indicated that mental decline can be caused by molecules leaking into the brain.
Blood vessels in the brain are different from those in other parts of the body. They protect the organ by allowing only nutrients, oxygen and some drugs to flow into the brain, but block larger, potentially damaging molecules. This is known as the blood-brain barrier.
The scans revealed that this barrier becomes increasingly leaky as we get older. For example, 30-40% of people in their 40s have some disruption to their blood-brain barrier, compared with 60% of 60-year-olds.
The scans also showed that the brain was inflamed in leaky areas.
Professor Daniela Kaufer, who leads the Berkeley group, said that young mice altered it to have leaky blood-brain barriers showed many signs of aging.
Professor Kaufer told BBC News that he has not only genetically altered young mice by showing signs of aging, it has reversed the signs of aging. In older mice.
"When you think about brain aging, you're thinking about degeneration of cells and losing what we have," she said.
"What these results show is that you are not losing anything. The cells are still there and they just needed to be 'unmasked' by reducing the inflammation."
Brain's weak link
In another study, Canadian Researchers also said that they could reverse cognitive decline in mice using an alternative approach.
They targeted a brain cell known to be a "weak link" in many brain disorders. The so-called somatostatin-positive neurons, which are involved in coding information, are the first to fail. The signals from these cells are too weak to be received by surrounding neurons, which would relay the information to other parts of the brain.
Prof. Etienne Sibille, from the University of Toronto, identified a chemical that essentially amplifies the signal. He presented results that showed that older mice who could not find their way around mazes could do that after they were given the chemical, just as well as younger pills not given the drug.
Prof. Sibille said he was hoping to begin clinical trials on human patients in two years' time.
"If people have a cognitive deficiency, we could potentially be able to bring them back to higher functioning."
The The big caveat is that the vast majority of treatments that show promise in mice do not work on humans. But both scientists believe that this time it may be different.
Prof Sibille said he was heartfelt by the fact that the chemical repaired damaged neurons when it was given to the mouse. And Prof Kaufer said she believed that such a work could really lead to a brain rejuvenation pill.
"People get jaded when they hear that things work on mice and then they are tried on humans," she said. "But I think there's something different and exciting about this story in that it explains a new biology."
"It looks at brain function in a different way. It's about mechanisms that have been neglected and not thought about before. "