- Getting enough sleep is an important part of a person’s overall health.
- Poor sleep is a risk factor for cognitive issues such as memory loss.
- Researchers from Charité – Universitätsmedizin Berlin have clarified what happens during deep sleep — also known as slow wave sleep — to support the formation of memories in the brain.
- The study adds to evidence showing sleep’s crucial role in memory consolidation, and may help scientists come up with preventive strategies against dementia.
Everyone knows that getting enough sleep is an important part of a person’s overall health.
Past studies show proper sleep can help improve a person’s
Sleep is also important for
“Depriving humans of sleep leads to all sorts of problems and can cause serious harm,” Franz Xaver Mittermaier, scientific staff member of the Institute of Neurophysiology at Charité – Universitätsmedizin Berlin in Germany, told Medical News Today.
“It is fair to argue that the organ that needs sleep the most is the brain. Sleep disconnects the brain from the outside world. The stream of sensory information is stopped. This allows for the replay of past experiences without ‘outside interference’ which is necessary to consolidate the memories of these experiences — i.e. move them into the long-term memory,” he said.
Mittermaier is the first author of a new study recently published in the journal
For this study, Mittermaier and his team used intact tissue samples of the
“The neocortex is the outermost part of the brain. Whenever we see a picture of the brain, the surface that we look at is the neocortex — the walnut-shaped surface. It is a structure that contains 16 billion neurons (electrically active brain cells). The neocortex is greatly enlarged in humans and plays a central role for the cognitive abilities that make us human: language, imagination, memory, emotion, etc.”
— Franz Xaver Mittermaier
“In 2017, we started to develop a platform, where we collect brain samples from neurosurgeries that would otherwise be discarded,” Mittermaier said. “We managed to improve our methods to keep these tissue samples alive for more than 24 in physiological solutions. This allows us to study human brain cells and connections between them (
“Once we had the ability to perform these recordings, memory mechanisms were a topic that was just very obvious to address. Prof. Geiger and Henrik Alle — a co-author of the current study — had
At the conclusion of the study, researchers found that the slow electrical waves created in the brain during deep sleep help to strengthen the synaptic connections between neurons in the neocortex, making it more “receptive” to forming memories.
“During deep slow-wave sleep, when the sensory stream from the outside world stops, the neocortex displays a very interesting activity that consists of UP- and DOWN-states that alternate approximately once per second,” Mittermaier explained. “UP- and DOWN-states result from synchronous changes in electrical voltage of many thousands of neurons in the neocortex.”
“We could show with our experiments that these UP- and DOWN-state sequences actually tune the synapses (i.e. the connections) between the brain cells and make (them) particularly strong when the neocortex changes from a DOWN-state to an UP-state,” he continued.
“The neocortex is put in a state of increased receptivity to information during that time-window. If the hippocampus — region of the brain that stores short-term memories — plays back a memory during this time-window, it leads to a more pronounced activation of neocortical brain cells, which in turn leads to a transfer into long-term storage,” he told MNT.
“We are only beginning to scratch the surface of the mechanisms that are actually at play when the brain sleeps. Furthermore, much of the research thus far has been in laboratory animals and not in human tissue samples (as in our study). We have lots of work to do to really understand the sleeping human brain. Our study is only the beginning. Understanding the sleeping brain will help us tackle disorders, such as memory impairment in the elderly.”
— Franz Xaver Mittermaier
MNT spoke with Verna Porter, MD, a board certified neurologist and director of the Dementia, Alzheimer’s Disease and Neurocognitive Disorders at Pacific Neuroscience Institute at Providence Saint John’s Health Center in Santa Monica, CA, who commented this study was both exciting and thought-provoking as it sheds light on the crucial role of slow wave activity (SWA) during deep sleep in synaptic plasticity and memory consolidation.
“The ability of SWA to strengthen synapses and stabilize memories at a precise, cellular level is particularly interesting,” Porter explained.
“For me, as a neurologist, this reinforces the critical importance of healthy sleep patterns in maintaining cognitive function. Given that patients with dementia often experience disrupted deep sleep, these findings underscore the need to better understand and address sleep deficits as part of dementia care and prevention.”
— Verna Porter, MD
“The next steps should focus on determining how SWA-driven synaptic mechanisms are altered in neurodegenerative diseases like Alzheimer’s and other forms of dementia. Longitudinal studies are needed to assess whether enhancing deep sleep can slow cognitive decline or improve memory retention in at-risk populations,” she continued.
MNT also spoke with Manisha Parulekar, MD, FACP, AGSF, CMD, director of the Division of Geriatrics at Hackensack University Medical Center and co-director of the Center for Memory Loss and Brain Health at Hackensack University Medical Center in New Jersey, about this study.
“Deep sleep, specifically slow-wave sleep, plays a crucial role in memory consolidation — the process of stabilizing and strengthening newly acquired memories. This study highlights possible pathways of sleep on memory and is outlining a potential mechanism to help improve memory consolidation.”
— Manisha Parulekar, MD, FACP, AGSF, CMD
“Dementia continues to be an important public health challenge. Studies are suggesting that the pathophysiology starts at much earlier time, 10 to 20 years before the cognitive symptoms. The findings could help identify possible preventative strategies and to explore treatment approaches that are intended to support memory formation,” Parulekar said.
“One next step could be further studies exploring the impact of cognitive behavioral therapy for insomnia (CBT-I), mindfulness-based stress reduction, sleep hygiene education, light therapy, and other noninvasive approaches on memory consolidation and its potential cognitive benefits,” she added.
