Sleep is critical for all sorts of reasons, but a team of international scientists has discovered a new incentive for getting eight hours of sleep every night: it helps the brain to store and learn a new language.
A study led by the University of South Australia (UniSA) and published in the Journal of Neuroscience has revealed that the coordination of two electrical events in the sleeping brain significantly improves our ability to remember new words and complex grammatical rules
In an experiment with 35 native English-speaking adults, researchers tracked the brain activity of participants learning a miniature language called Mini Pinyin that is based on Mandarin but with similar grammatical rules to English.
Half of the participants learned Mini Pinyin in the morning and then returned in the evening to have their memory tested. The other half learned Mini Pinyin in the evening and then slept in the laboratory overnight while their brain activity was recorded. Researchers tested their progress in the morning.
Those who slept performed significantly better compared to those who remained awake.
Lead researcher Dr Zachariah Cross, who did his PhD at UniSA but is now based at Northwestern University in Chicago, says sleep-based improvements were linked to the coupling of slow oscillations and sleep spindles - brainwave patterns that synchronise during NREM sleep.
"This coupling likely reflects the transfer of learned information from the hippocampus to the cortex, enhancing long-term memory storage," Dr Cross says.
"Post-sleep neural activity showed unique patterns of theta oscillations associated with cognitive control and memory consolidation, suggesting a strong link between sleep-induced brainwave co-ordination and learning outcomes."
UniSA researcher Dr Scott Coussens says the study underscores the importance of sleep in learning complex linguistic rules.
"By demonstrating how specific neural processes during sleep support memory consolidation, we provide a new perspective on how sleep disruption impacts language learning," Dr Coussens says. "Sleep is not just restful; it's an active, transformative state for the brain."
The findings could also potentially inform treatments for individuals with language-related impairments, including autism spectrum disorder (ASD) and aphasia, who experience greater sleep disturbances than other adults.
Research on both animals and humans shows that slow oscillations improve neural plasticity - the brain's ability to change and adapt in response to experiences and injury.
"From this perspective, slow oscillations could be increased via methods such as transcranial magnetic stimulation to accelerate aphasia-based speech and language therapy," Dr Cross says.
In future, the researchers plan to explore how sleep and wake dynamics influence the learning of other complex cognitive tasks.
"Understanding how the brain works during sleep has implications beyond language learning. It could revolutionise how we approach education, rehabilitation, and cognitive training."
Notes for editors
"Slow oscillation-spindle coupling predicts sequence-based language learning" is authored by scientists from the University of South Australia; Northwestern University, Chicago; University of Tübingen, Germany; Monash University; University of Adelaide; University of York, United Kingdom; and UC Berkeley, United States. DOI: 10.1523/JNEUROSCI.2193-23.2024
Mini Pinyin contains 32 verbs and 25 nouns, including 10 human entities, 10 animals and five objects. Overall, the language contains 576 unique sentences.
