Sounds that are in sync with the brain's slow oscillations help enhance memory, a new study reported. Slow oscillations in the brain occur during slow-wave sleep and are associated with memory. The sound stimulations can also help a person sleep better.

"The beauty lies in the simplicity to apply auditory stimulation at low intensities-an approach that is both practical and ethical, if compared for example with electrical stimulation-and therefore portrays a straightforward tool for clinical settings to enhance sleep rhythms," said Dr. Jan Born, of the University of Tübingen, in Germany, co-author of the study.

The study included 11 participants who were exposed to sound simulations or placebo simulations during sleep on different nights. Before the participants went to sleep, they were asked to memorize word association.

Researchers found that when participants were exposed to sounds that synchronized with the brain's slow oscillation rhythm, they were better at remembering the word association than when they were exposed to sounds that weren't in sync.

"Importantly, the sound stimulation is effective only when the sounds occur in synchrony with the ongoing slow oscillation rhythm during deep sleep. We presented the acoustic stimuli whenever a slow oscillation "up state" was upcoming, and in this way we were able to strengthen the slow oscillation, showing higher amplitude and occurring for longer periods," said Dr. Born in a news release.

The study is published in the journal Neuron.

Many studies have shown how sleeping affects recall of information. Complex motor skills can be learned by taking naps. Taking breaks during tasks gives better results, says a study that was published in 2010 in the journal Neuron. Another study has shown that brief amount of sleep after learning preserves memories that, at times, last for years.