The notion that we can learn in our sleep is a captivating idea. Imagine the possibility – that we could really be capable of drastically improving our productivity by learning in our sleep… you have to admit, it is very appealing! The reality is, sleeping time is mostly considered unproductive time.
Not anymore! A recent study finds that it may be possible to learn new vocabulary during deep sleep. It appeared that memory formation was mediated by the same sort of brain structures that mediate wake vocabulary learning. The researchers found that during distinct phases of slow-wave sleep we can attain the vocabulary of a new language. Consequently, this sleep-learned vocabulary could be retrieved consciously following waking.
There were previous studies that show that by replaying something learned while awake (wake-learned information) when you sleep, helps to strengthen the still fragile memory traces thus embedding the newly acquired information in the preexisting store of knowledge. This study is published in the journal Current Biology. Yet, for someone to learn something new while sleeping was still unknown knowledge.
For the new research, they figured “If re-play during sleep improves the storage of wake-learned information, then first-play — i.e., the initial processing of new information — should also be feasible during sleep, potentially carving out a memory trace that lasts into wakefulness.” Katharina Henke is the Marc Züst und Simon Ruch of the Institute of Psychology and of the Interfaculty Research Cooperation “Decoding Sleep” at the University of Bern, Switzerland who decided to research this question.
“Decoding Sleep” is a large, interdisciplinary research project that is financed by the University of Bern, Switzerland. Thirteen research groups in medicine, biology, psychology, and informatics are part of the IRC. The aim of these research groups is to gain a better understanding of the mechanisms involved in sleep, consciousness, and cognition.
Henke and a group of investigators found that people could reactivate the sleep-formed associations to access word meanings when represented with the formerly sleep-played foreign words. Their experiments reveal that the hippocampus, a brain structure essential for wake associative learning, also supported the retrieval of sleep-formed associations in the participants. The results are published in the scientific journal Current Biology.
“When we reach deep sleep stages, our brain cells progressively coordinate their activity. During deep sleep, the brain cells are commonly active for a brief period of time before they jointly enter into a state of brief inactivity. The active state is called “Up-state” and the inactive state “Down-state.” The two states alternate about every half-second.”
The study involved a group of 41 German-speakers. The researchers found that they could add words, made-up words in this case, to the participants’ brains while they napped. For example, they used the made-up word “topher” which was paired with the German word for “key”, and “guga” was linked to the word for “elephant”. Each word was played for times, matching the rhythm of the sleeping brain so that the second word coincided with the up-states. Altogether, the participants heard about 36 distinct word pairs with over 146 repetitions.
“The time point when the second word of a pair was played was crucial, because this was the moment when a word-word association could be formed, and therefore when neural plasticity needs to be optimal,” the authors explained.
Upon waking, the researchers showed the volunteers the made-up words and were asked to picture if the object was smaller or larger than a shoebox. They found that participants correctly characterized the made-up words with their paired words 10 percent higher than chance.
Theoretically, a person could learn new words from another language in this same way. However, it’s not that easy. The researchers specifically focused the timing of the words with up- and down-states lasting just 2 seconds using an EEG brain scan, and they believe that it is only in this specific deep-sleep state that isn’t associated with dreaming that learning new words is possible.
Simon Ruch, co-author of the study, believes that “We could disprove that sophisticated learning be impossible during deep sleep.” Henke adds, “In how far and with what consequences deep sleep can be utilized for the acquisition of new information will be a topic of research in upcoming years.”