Deep, uninterrupted sleep improves memory
Many people are very good at remembering faces but are terrible at remembering names. A recent Northwestern University study may have found the remedy: a power nap. The work has just been published in the journal ‘ NPJ: Science of Learning ‘.
The human brain never stops while it lives, not even when it sleeps. In fact, the neuronal activity that takes place during deep sleep is not much less than during wakefulness, although it has a different structure: during deep sleep, the information acquired during the day is ‘consolidated’, possibly because the neurons communicate between them in a peculiar way, in synchrony.
Now, this new experiment documents how recalling memory right while sleeping through external stimuli could be key in remembering names.
The test was carried out with 24 participants between the ages of 18 and 31, who were asked to memorize the faces and names of 40 students from a hypothetical Latin American history class and as many from another Japanese history class. When each face was shown again, they were asked to indicate the corresponding name. After the learning exercise, the participants took a nap while the researchers carefully monitored brain activity using EEG measurements (a recording of the brain’s electrical activity picked up by electrodes on the scalp). When the analyzes indicated that the participants were in phase N3-in which there is very deep and restorative sleep, with the presence of brain delta waves, absence of eye movements, slow heart rate and breathing, absence of dreams, and just before what is known as the REM phase -, some of the names were softly repeated along with music associated with the classes.
When the participants woke up, they were retested to recognize the faces and remember the name that went with each face. The team found that for study participants with EEG measurements indicating disrupted sleep, memory reactivation did not help and even worsened their memory. However, for those who did not wake up to the sound in this phase, reactivation led to a relative improvement with a mean almost 1.5 points higher, so the key, according to the authors, lies in reaching a dream continuously deep.
“This is an exciting new finding because it tells us that the way information is reactivated during sleep to enhance memory storage is related to high-quality sleep,” says lead author Nathan Whitmore, a researcher at the University of Northwestern. “We already know that some sleep disorders such as apnea can affect memory. Our research suggests a possible explanation for this: frequent sleep interruptions at night could be degrading memory.”
The experiment does not want to end there, as it wants to delve into how to reactivate memories and deliberately interrupt sleep to learn more about the relevant brain mechanisms. “This new line of research will allow us to address many exciting questions, such as whether sleep disruption is always harmful or could be used to weaken unwanted memories,” said Ken Paller, professor of psychology and director of the Cognitive Neuroscience Program at the Weinberg College of Arts and Sciences at Northwestern. “In any case, we find more and more good reasons to value high-quality sleep.”
