https://www.nature.com/articles/d41586-024-01732-y Skip to main content Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript. Advertisement Advertisement Nature * View all journals * Search * Log in * Explore content * About the journal * Publish with us * Subscribe * Sign up for alerts * RSS feed 1. nature 2. news 3. article * NEWS * 12 June 2024 Sleep deprivation disrupts memory: here's why Study in rats shows that a key brain signal linked to memory formation deteriorates after broken sleep. By * Max Kozlov 1. Max Kozlov View author publications You can also search for this author in PubMed Google Scholar * Twitter * Facebook * Email A fluorescence light micrograph of brain hippocampus neurons, shown in green and blue Neurons (artificially coloured) in the hippocampus play a part in learning and memory.Credit: Cell Applications Inc/Science Photo Library A crucial brain signal linked to long-term memory falters in rats when they are deprived of sleep -- which might help to explain why poor sleep disrupts memory formation^1. Even a night of normal slumber after a poor night's sleep isn't enough to fix the brain signal. These results, published today in Nature, suggest that there is a "critical window for memory processing", says Loren Frank, a neuroscientist at the University of California, San Francisco, who was not involved with the study. "Once you've lost it, you've lost it." In time, these findings could lead to targeted treatments to improve memory, says study co-author Kamran Diba, a computational neuroscientist at the University of Michigan Medical School in Ann Arbor. Firing in lockstep Neurons in the brain seldom act alone; they are highly interconnected and often fire together in a rhythmic or repetitive pattern. One such pattern is the sharp-wave ripple, in which a large group of neurons fire with extreme synchrony, then a second large group of neurons does the same and so on, one after the other at a particular tempo. These ripples occur in a brain area called the hippocampus, which is key to memory formation. The patterns are thought to facilitate communication with the neocortex, where long-term memories are later stored. One clue to their function is that some of these ripples are accelerated re-runs of brain-activity patterns that occurred during past events. For example, when an animal visits a particular spot in its cage, a specific group of neurons in the hippocampus fires in unison, creating a neural representation of that location. Later, these same neurons might participate in sharp-wave ripples -- as if they were rapidly replaying snippets of that experience. [d41586-024] Unpicking the link between smell and memories Previous research^2 found that, when these ripples were disturbed, mice struggled on a memory test. And when the ripples were prolonged, their performance on the same test improved^3, leading Gyorgy Buzsaki, a systems neuroscientist at NYU Langone Health in New York City, who has been researching these bursts since the 1980s, to call the ripples a 'cognitive biomarker' for memory and learning. Researchers also noticed^4 that sharp-wave ripples tend to occur during deep sleep as well as during waking hours, and that those bursts during slumber seem to be particularly important for transforming short-term knowledge into long-term memories^5. These links between the ripples, sleep and memory are well-documented, but there have been few studies that have directly manipulated sleep to determine how it affects these ripples, and in turn memory, Diba says. Wake-up call To understand how poor sleep affects memory, Diba and his colleagues recorded hippocampal activity in seven rats as they explored mazes over the course of several weeks. The researchers regularly disrupted the sleep of some of the animals and let others sleep at will. To Diba's surprise, rats that were woken up repeatedly had similar, or even higher, levels of sharp-wave-ripple activity than the rodents that got normal sleep did. But the firing of the ripples was weaker and less organized, showing a marked decrease in repetition of previous firing patterns. After the sleep-deprived animals recovered over the course of two days, re-creation of previous neural patterns rebounded, but never reached levels found in those which had normal sleep. [d41586-024] Memories are made by breaking DNA -- and fixing it This study makes clear that "memories continue to be processed after they're experienced, and that post-experience processing is really important", Frank says. He adds that it could explain why cramming before an exam or pulling an all-nighter might be an ineffective strategy. It also teaches researchers an important lesson: the content of sharp-wave ripples is more important than its quantity, given that rats that got normal sleep and rats that were sleep-deprived had a similar number of ripples, he says. Ripple effects Buzsaki says that these findings square with data his group published in March^6 that found that sharp-wave ripples that occur while an animal is awake might help to select which experiences enter long-term memory. It's possible, he says, that the disorganized sharp-wave ripples of sleep-deprived rats don't allow them to effectively flag experiences for long-term memory. As a result, the animals might be unable to replay the neural firing of those experiences at a later time. This means that sleep disruption could be used to prevent memories from entering long-term storage, which could be useful for people who have recently experienced something traumatic, such as those with post-traumatic stress disorder, Buzsaki says. doi: https://doi.org/10.1038/d41586-024-01732-y References 1. Giri, B. et al. Nature https://doi.org/10.1038/s41586-024-07538-2 (2024). Article Google Scholar 2. Jadhav, S. P., Kemere, C., German, P. W. & Frank, L. M. Science 336, 1454-1458 (2012). Article Google Scholar 3. Fernandez-Ruiz, A. et al. Science 364, 1082-1086 (2019). Article Google Scholar 4. Eschenko, O., Ramadan, W., Molle, M., Born, J. & Sara, S. J. Learn. Mem. 15, 222-228 (2008). Article PubMed Google Scholar 5. Ramadan, W., Eschenko, O. & Sara, S. J. PLoS ONE 4, e6697 (2009). Article Google Scholar 6. Yang, W. et al. Science 383, 1478-1483 (2024). 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Montreal, Quebec (CA) Prof. A. Claudio Cuello [] You have full access to this article via your institution. Download PDF Related Articles * [d41586-024] How better sleep can improve productivity * [d41586-024] Sleep loss impairs memory of smells, worm research shows * [d41586-024] How to freeze a memory: putting worms on ice stops them forgetting * [d41586-024] Memories are made by breaking DNA -- and fixing it * [d41586-024] Brain stimulation leads to long-lasting improvements in memory Subjects * Brain * Neuroscience Advertisement Sign up to Nature Briefing An essential round-up of science news, opinion and analysis, delivered to your inbox every weekday. Email address [ ] [ ] Yes! Sign me up to receive the daily Nature Briefing email. I agree my information will be processed in accordance with the Nature and Springer Nature Limited Privacy Policy. Sign up * Close Nature Briefing Sign up for the Nature Briefing newsletter -- what matters in science, free to your inbox daily. 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