Poor memory due to aging can be reversed, according to researchers who found that elderly, more forgetful mice regained the memory abilities of younger mice when levels of an enzyme, that switches genes on or off in the brain, were increased.

Scientists found that after receiving extra amounts of the DNA methyltransferase, older mice performed just like younger mice in memory tests, according to a new study published in the journal Nature Neuroscience.

Researchers from the University of Heidelberg had injected a virus that contains extra copies of the gene responsible for creating DNA methyltransferase into the hippocampus, area of the brain responsible for memory, of elderly mice that were showing signs of diminished memory.

Afterwards, the team gave the mice a series of memory tests such as showing the mice a new object to investigate for a period of time, taking it away and presenting them with the same object the next day along with another new object.

Past studies showed that younger more able-minded mice will immediately begin investigating the newer object, while older mice will spend equal amounts of time investigating both objects, having seemingly forgotten that they'd already seen the object the day before.

The research team found that once the older mice were injected with the virus, the elderly mice had spent most of their time, 70 percent of the time, investigating the new object, suggesting that an increase of the enzyme restored their faulty memories to its original capacity.

However, when researchers halved the amount of DNA methyltransferase produced by younger mice, the memory abilities deteriorated to that of non-treated older mice.

"Clearly, if you have too little of the enzyme, your memory works less well," co-author Hilmar Bading of the University of Heidelberg in Germany told New Scientist.

Researchers noted that because of differences in physiology, there is no way to try the same experiment on people, but they are looking into other ways to change the levels of DNA methyltransferase in humans to see if the change might produce similar memory-enhancing results.

Researchers said that in the meantime, people should do their best to keep their brain and bodies active as they age because doing so tends to naturally increase maintain levels of the enzyme that decreases with aging.