Scientists have revealed through a new study that brainwaves produced during sleep strengthen memories by storing new information in our memory.
For decades the relation between sleep and memory has been known and now the new study published in the journal NeuroImage helps us know better how learned information turns into reliable memories during sleep. Scientists from Concordia University in Canada and University of Liege in Belgium studied how declarative information like facts and faces get stored after they have been learned.
Brainwaves—specifically, ones called sleep spindles, are fast bursts of electrical activity produced by neurons mainly during Stage 2 sleep, prior to deep sleep. Using medical imaging machines, researchers were able to assess brain activity related to these waves.
To get the images they needed, the team used both electroencephalography (EEG) and functional magnetic resonance imaging (fMRI). They applied these tools to a group of student volunteers during and after a lab-based face-sequencing task. The students were shown a series of faces and asked to identify the order in which they were shown.
The researchers scanned them while they were learning the faces, while they were asleep and again when they woke up and had to recall the sequences.
They then came back every day for a week and repeated the task without being scanned. After a week had elapsed, they had memorised the task, and were once again scanned during sleep and asked to recall the sequences.
The researchers found that during spindles of the learning night, the regions of the brain that were instrumental in processing faces were reactivated.
They also observed that the regions in the brain involved in memory—especially the hippocampus—were more active during spindles in the subjects who remembered the task better after sleep.