Stimulation applied to a brain area known to be important for math ability has been shown to improve the ability to manipulate numbers, British researchers say.

"With just five days of cognitive training and noninvasive, painless brain stimulation, we were able to bring about long-lasting improvements in cognitive and brain functions," Roi Cohen Kadosh of the University of Oxford reported in the journal Current Biology.

While the researchers acknowledge no one knows exactly how the relatively new technique -- transcranial random noise stimulation -- works, they say the evidence suggests it allows the brain to work more efficiently by making neurons fire more synchronously.

The technique improves mental arithmetic -- the ability to add, subtract or multiply a string of numbers in one's head, for example -- not just new number learning, the researchers said.

Mental arithmetic is a more complex and challenging task, which more than 20 percent of people struggle with, they said.

The stimulation technique could be of particular help to those suffering with neurodegenerative illness, stroke or learning difficulties, Cohen Kadosh said.

"Math is a highly complex cognitive faculty that is based on a myriad of different abilities," he said. "If we can enhance mathematics, therefore, there is a good chance that we will be able to enhance simpler cognitive functions."