Mice study raises hope for regaining Memory loss

US researchers have found cure for lost memories in mice, raising hope for developing new treatments for people suffering from neuro-degenerative diseases, including Alzheimer's disease, and suggesting a way to restore lost memories by natural 'rewiring' of brain cells.

In the study, researchers used mice that were bioengineered to mimic the fading memory of Alzheimer's patients. The genetically modified mice produce a protein (p25) when fed an antibiotic. Previous studies have suggested that the protein p25 is associated with brain cell death.

Study’s lead author Li-Huei Tsai, a professor of brain and cognitive sciences at the Massachusetts Institute of Technology's Picower Institute of Learning and Memory and colleagues, who reported their study with mice on April 29 in the online edition of the journal Nature, suggested that toss of memory in people suffering from neuro-degenerative diseases, including dementia, may be restored with the help of drugs that trigger the natural 'rewiring' of brain cells.

Although the research is in its preliminary stage, still it provides hope for human patients, especially those with dementia, Li-Huei Tsai said.

Before starting their study with the mice, researchers first placed the mice in a tank of water and trained them to find their way to a platform sunk just below the surface. After the mice had developed a long-term memory of the job, Tsai's team then induced p25 in the rodents, which led to loss of neurons, learning ability and memory.

The mice were placed in a setting full of toys and wheels. When the stimulated mice were retested, the researchers found they did better at the memory task than before.

In order to reverse memory loss in mice with a condition like Alzheimer's, researchers used two methods, first by placing them in sort of a rodent Disneyland to stimulate their brains, and secondly using a type of drug that encourages growth of brain nerve cells.

In one part of their study, the scientists took mice out of their usual bland cages and placed them in an "enriched" environment - rooms full of shelves, perches, nesting material, tunnels and (especially) other mice.

Researchers found that these playground mice were still able to use their memory to find their way through mazes they had learned to navigate weeks before, while the mice kept in un-stimulating surroundings typically got lost and failed to complete tasks. These rodents were apparently unable to remember tasks they had learned before, including navigating the mazes, the researchers’ team said.

"If memories can be recovered then that suggests they were never erased and indicates that perceived memory loss is likely to be due to an inability to retrieve memories," Tsai said.

After exploring the biological mechanism behind the improvement in mice placed in the enriched environment, the researchers took mice that had lost long-term memory and injected them with a drug that inhibited histone deacetylase, or HDAC.

When tested, the team found that memory and learning improved in the mice, similar to improvements caused by environmental stimulation. These mice were better able to find the platform in the water, researchers said.

Tsai said that HDAC inhibitors appear to cause naturally the rewiring of neurons. "If we could use drugs to facilitate that process I believe it would be very beneficial to people suffering from advanced stages of neurodegeneration," she said.

Alzheimer's disease is the most frequent type of dementia in the elderly and affects almost half of all patients with dementia. The most striking early symptom of Alzheimer’s is loss of short term memory.

As the disorder progresses, cognitive injury extends to the domains of language (aphasia), skilled movements (apraxia), recognition (agnosia), and those functions (such as decision-making and planning) closely related to the frontal and temporal lobes of the brain.

In 2004, Alzheimer’s was the 7th leading cause of death in USA, with 65,829 numbers of deaths. AD is the third most costly disease in the U.S., after heart disease and cancer. The average lifetime cost of care for an individual with Alzheimer’s is $174,000.

It has been projected that by 2040, the number of people suffering from AD will shoot up to 81 million, unless new ways are found to prevent or treat the disease. According to the Alzheimer's Association, five million people in the United States currently suffer from the illness.