Anyone who has ever tucked a small child to bed or into a gently rocking hammock will know that a rocking motion makes it easier to fall asleep. Now, a new study conducted in young adults proves the broad benefits of rocking motion during sleep. In fact, the study in humans shows that rocking not only leads to better sleep, but also to memory consolidation during sleep.
The researchers had previously shown that continuous rocking during a 45-minute nap helped people fall asleep faster and sleep better. In the new study, they wanted to explore the effects of rocking on sleep and its associated brain waves during the night.
The researchers recruited 18 healthy young adults to undergo sleep monitoring in the lab. The first night was meant to get them used to sleeping there. Then they stayed for two more nights – one sleeping on a gently rocking bed and the other on an identical bed that didn't move.
The data showed that participants fell asleep faster while rocking. Once asleep, they also spent more time with non-fast eye movement sleep, slept more deeply and woke up less.
Next, the researchers wanted to know how that better sleep affected memory. To assess memory consolidation, the participants studied word pairs. The researchers then measured their accuracy in remembering those paired words in an evening session compared to the next morning when they woke up. They found that people did better on the morning test when they rocked at bedtime.
Further studies have shown that rocking affects brain oscillations during sleep. They saw that the rocking motion caused an entrainment of specific brain vibrations from non-fast eye movement sleep (slow oscillations and spindles). As a result, the continuous rocking motion helped to synchronize neural activity in the brain's thalamo-cortical networks, which play an important role in both sleep and memory consolidation.
