How does sleep affect memory?

11 Jul, 2019

Since ancient times, parents have rocked their babies to sleep in their arms or rocked a crib in a lulling motion and this has sent their babies into a deep sleep. Ever wondered why?

Study 1

A Swiss research team performed a study where they made a bed that was attached to the roof on ropes like a swing almost, and after the participants were asleep having a nap they pulled on the ropes to move the bed from side to side at the same speed. Half the group had their beds swung when they entered NREM sleep (measured through electrodes on their heads) and the other half had the bed stay still. What they found was that the the slock rocking had lots of benefits:

It increased the depth of deep sleep
improved quality of slow brainwaves
doubled sleep spindles

What we know is that the more sleep spindles you have the better you remember and learn things from the previous day in your short term memory.

Study 2

A German research team also did a study on the effect of electrical brainwaves on sleep. They basically waited for the participants to go into nREM sleep and then switched on these stimulators that would send slow waves pulsating into their brain in time with the nREM waves. What the found was:

the size of the slow brainwaves increased during stimulation
the number of sleep spindles increased during stimulation
after waking up, the participants who had electrical brainwaves being transmitted into their brain during sleep had remembered double the number of facts than the control group who didn’t have electrical voltage pulses on their brain.

Other ways of doing this without risking burning yourself or shocking yourself is a study that played quiet tick tock tones in time with your brainwaves to retrain the sleep rhythm and produce deeper sleep. This resulted in 40% memory enhancement.

But be warned - if you get the timing wrong it could actually disrupt your sleep and make it worse.

Targeted Memory Reactivation

This is a little off topic to rocking your child but hear me out. Matthew WAlker discusses the process of targeted memory reactivation for adults where they show participants indivudal pictures on a screen with a corresponding sound. After you sleep and are shown a number of pictures the next day, you have to decide which of them were on your screen and which were not. But researchers can select which items you remember by playing the sounds to you in your sleep for the specific objects they want you to remember using their auditory tag.

For example, you see hundreds of pictures such as a dog with a ‘woof’ noise, a cat with a ‘meow’ noise a bell with a ‘ding-a-ling’ noise and a swing with a ‘swoosh’ noise. The researchers want you to remember the dog and the swing, so they will play woof and swoosh to you while you are in NREM sleep.

When you wake up in the morning you will remember much more of the pictures that had an auditory tag played to you in your sleep like dog (for woof) and swing (for swoosh), than the ones that were not played to you.

How does this impact our babies? They are learning so much!

I’m not suggesting you try this but consider the impact of what we say to our babies while they are awake, pointing out objects and enunciating words, and think about how much more ingrained they would be in our child’s memory the next day if we repeated these words whilst they were asleep, targeting specific memories to be reactivated and moved from short term to long term storage over night.

Matthew Walker has a lot more information on his book on the importance of sleeping the night before learning and the night after learning. Check out his book if this is of interest to you, particularly if you have teenagers who aren’t sleeping enough and are at a critical time where they are learning so much and functioning on very little sleep and a lot of caffeine.

Research