Sleep sounds 'boosted memory'

Scientists used stimulating sounds carefully timed to follow the slow oscillating brainwaves generated during deep sleep. Photo: Neuron/PA

Memories can be boosted during sleep by playing sounds synchronised with brainwaves, a study has shown.

The technique was used to help 11 slumbering volunteers remember word associations learned the evening before.

Scientists used stimulating sounds carefully timed to follow the slow oscillating brain waves generated during deep sleep.

“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,” said Jan Born, from the University of Tubingen in Germany.

During the experiments, the effect of synchronised sounds was compared with that of non-synchronised sounds.

Volunteers were played bursts of “pink noise” – a hissing sound containing a particular range of frequencies.

Stimulating sounds boosted the memory of participants the next day, while sounds out of phase with the brain waves had no effect.

The findings are reported online in the journal Neuron.

“Importantly, the sound stimulation is effective only when the sounds occur in synchrony with the ongoing slow oscillation rhythm during deep sleep,” said Born.

The sounds also had the effect of strengthening the brain wave rhythm, he added, suggesting that the approach could be used to improve quality of sleep.

“Moreover, it might be even used to enhance other brain rhythms with obvious functional significance – like rhythms that occur during wakefulness and are involved in the regulation of attention,” Born added.