The same brain mechanisms that record memory while awake make an appearance during sleep.
A new study published by Dutch and British researchers reports that being awake and forming memories is just half the story -- you also need to sleep and consolidate them. Surprisingly, however, the same brain networks and mechanisms that formed the memory are reactivated during its consolidation.
"Understanding how memories are reactivated in different states also provides insight into how these memories could be altered -- which might for example be interesting in therapeutic settings," says co-lead author Dr. Tobias Staudigl, of the Donders Institute in Holland.
Sleep is very important for the formation of stable, long-lasting memories. Researchers -- as well as students during finals -- have been aware of this for some time now, but we've never really had a good look at how our brains process memories during sleep.
Donders' team set out to record and study these processes using a technique called Targeted Memory Reactivation, which is known to enhance memory. Boiled down, the technique involves playing back previously learned information (in this case words in a foreign language) to a person while they are sleeping.
The researchers used electroencephalography to monitor the brain activity of each participant while they were learning and remembering the foreign vocabulary before sleep. Participants' brain activity was recorded as they were sleeping, allowing the team to see what brain pathways activated upon them hearing the words.
Comparing neural signals fired by the brain in each state, the researchers were able to show clear similarities in brain activity.
"Although sleep and wakefulness might seem to have little in common, this study shows that brain activity in each of these states might be more similar than we previously thought," says lead author Dr. Thomas Schreiner, of the University of Birmingham's School of Psychology.
"The neural activity we recorded provides further evidence for how important sleep is to memory and, ultimately, for our well-being."
In the future, the team plans to follow up on their research by investigating spontaneous memory activation during sleep.
So, students the world over, science has spoken: pulling an all-nighter to cram up just isn't a very good way to study. If it's daytime, glue yourself to the book; at night, that head needs to go on a pillow.
The paper "Theta Phase-Coordinated Memory Reactivation Reoccurs in a Slow-Oscillatory Rhythm during NREM Sleep" has been published in the journal Cell Reports.