Everyone knows sleep is essential for good health. Despite decades and decades of research, we’ve still not uncovered the exact role sleep plays in the human body. Now, new research shows sleep is important for one of our most complex abilities — learning a new language. A study led by the University of South Australia (UniSA) reveals that sleep helps the brain retain new words and master grammar, providing a deeper understanding of why eight hours of shut-eye may be important for linguistic success.

The Sleep-Language Connection

In the study, 35 English-speaking adults were tasked with learning a miniature language called Mini Pinyin. Based on Mandarin but simplified to mirror English grammar, Mini Pinyin featured a set of verbs, nouns, and 576 unique sentences designed to challenge the participants’ memory and cognitive skills.

Participants were split into two groups. One group learned the language in the morning and returned in the evening for a test. The other group learned in the evening and stayed overnight in a sleep lab, where their brain activity was monitored during non-rapid eye movement (NREM) sleep. When tested in the morning, the sleepers significantly outperformed their awake peers.

The secret, according to lead researcher Dr. Zachariah Cross, lies in the brain’s ability to coordinate two electrical patterns: slow oscillations and sleep spindles.

“This coupling likely reflects the transfer of learned information from the hippocampus to the cortex, enhancing long-term memory storage,” he says.

In simpler terms, these rhythms help move new knowledge into the brain’s permanent storage system.

A new chapter in sleep research

The findings underscore the importance of sleep for consolidating memory, particularly for complex tasks like language learning. Previous studies indicate that sleep facilitates the consolidation of both declarative (explicit) and procedural (implicit) memories. Slow-wave sleep (SWS), a deep sleep stage, is primarily associated with consolidating declarative memories, such as facts and events. In contrast, rapid eye movement (REM) sleep is linked to the consolidation of procedural memories, which involve skills and tasks.

Sleep deprivation impairs attention, working memory, and the ability to learn new tasks. Conversely, sufficient sleep improves cognitive performance and learning outcomes, according to the Perelman School of Medicine at the University of Pennsylvania.

Dr. Scott Coussens, a co-author of the new study, adds that sleep isn’t just restful — it’s transformative. “By demonstrating how specific neural processes during sleep support memory consolidation, we provide a new perspective on how sleep disruption impacts language learning,” he says.

These insights could have far-reaching applications. People with language-related impairments, such as those with autism spectrum disorder or aphasia, often face sleep disruptions that hinder learning. The study suggests that therapies targeting slow oscillations—perhaps using methods like transcranial magnetic stimulation — could accelerate recovery and improve cognitive training outcomes.

Past research has shown that slow oscillations are linked with neuroplasticity, the brain’s ability to adapt and rewire itself.

“Understanding how the brain works during sleep has implications beyond language learning. It could revolutionize how we approach education, rehabilitation, and cognitive training,” said Dr. Cross.

The team is already planning future studies to explore how sleep dynamics influence other types of complex learning. For now, what we know is that sleep shapes how we learn, remember, and grow.

The findings appeared in the Journal of Neuroscience.