In a new study, researchers found that gentle sounds played during specific times during sleep could enhance deep or slow-wave sleep.
The effect is strong in older people with mild cognitive impairment, a warning sign for Alzheimer’s disease.
In addition, the people whose brains responded the most robustly to the sounds showed improved memory in the following day.
The research was conducted by a team from Northwestern University.
Deep sleep is critical for memory consolidation. Several sleep disturbances have been observed in people with mild cognitive impairment.
The biggest changes include a reduced amount of time spent in the deepest stage of sleep.
The team previously had found that that sound stimulation improved memory in older adults.
In the new study, the team tested sound stimulation overnight in nine people with mild cognitive impairment.
Participants spent one night in the sleep laboratory and another night there about one week later. Each participant received sounds on one of the nights and no sounds on the other.
The sound stimulation consisted of short pulses of pink noise, similar to white noise but deeper, during the slow waves.
The people did memory testing the night before and again in the morning.
The researchers found that the people who had an increase in their slow wave activity after the sound stimulation could remember more words.
In addition, there was a strong relationship between the enhancement of deep sleep by sound and memory: the greater the deep sleep enhancement, the better the memory response.
These findings show that slow-wave or deep sleep may be an important way to benefit people with mild cognitive impairment.
The team hopes the study can help develop new treatment of mild cognitive impairment and Alzheimer’s disease.
In the future, the team plans to evaluate pink noise stimulation in a larger sample of people with mild cognitive impairment over multiple nights to confirm the findings.
The lead author of the study is Dr. Roneil Malkani, assistant professor of neurology at Northwestern University.
The study is published in the Annals of Clinical and Translational Neurology.
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