According to German scientists, mild electric stimulation of the brain while asleep improves a person's memory. Jan Born, a neuroscientist at the University of LŁbeck , Germany and his team conducted a study in which, they applied currents that mimic natural slow oscillating brain waves through electrodes attached to the scalp.
13 medical students who were involved in the study were made to learn a list of paired words in a standard memory test before they slept. Their brain was stimulated while they were asleep. The students were asked to recall the words they had memomorised once they got up.
The findings revealed that without the electric stimulation, the students remembered an average of 37.42 words before sleep and 39.5 words on waking up. On the other hand, electric stimulation increased the average to 41.27 after sleep.
"This is proof that this slow oscillation has a real function during sleep -- to build and consolidate memory," said Born.
"It is an eight percent increase overall. This is a striking increase," he added.
There were no adverse side effects due to the current applied to the frontal cortex of the brain. The scientists reported that the current made the brain move into the deep slow-wave sleep. At this stage, there are normal electric fluctuations in the prefrontal neocortex that is associated with conscious thought and spatial reasoning.
In the study, no memory enhancement was noticed when current applied was of a different frequency or was applied at a different stage of sleep. The reasons are still not clear.
"One plausible theory is that electrical currents of a particular frequency can make brain cells resonate. This strengthens connections between networks of cells, which are the physical representations of memories in the brain, " said Born.
This study was published in the online edition of the journal Nature.
Scientists believe that brain stimulation could also help people with Alzheimer's disease.