- Sleep is essential for overall health and well-being.
- Previous research links good sleep with myriad benefits, such as improved memory and cognition.
- Researchers from Tel Aviv University and UCLA Health have uncovered more information on how the brain consolidates memory during sleep.
- Scientists found that deep brain stimulation applied during the deepest sleep cycle improves the brain’s ability to make memories.
Sleep is an important part of the body’s daily process and is essential for good health.
Now, researchers from Tel Aviv University and UCLA Health have found evidence supporting the dominant theory of how the brain consolidates memory during sleep.
The study was recently published in the journal
When a person sleeps, their body goes through four different stages:
- Stage 1: When a person starts to fall asleep and includes light
non-rapid eye movement (REM)sleep.
- Stage 2: Deeper non-REM sleep as the body continues to relax.
- Stage 3: Non-REM deep sleep stage and is the longest sleep stage.
- Stage 4: REM sleep — when a person has their most vivid dreams and is the closest stage to waking up.
Normally it takes about an hour from falling asleep for a person to enter the deep sleep stage. It is very hard for a person to wake up during this stage.
During deep sleep, brain waves are at their slowest, allowing the brain to relax and recover. Researchers also believe deep sleep plays an important role in healthy
Sleep deprivation can cause a number of issues, including fatigue, irritability, and difficulty with focusing or remembering.
Long-term sleep deprivation has been linked to an increased risk of:
Deep-brain stimulation may be used as a treatment for certain types of brain disease, including:
epilepsy Parkinson’s diseas e ( P D) essential tremor dystonia Tourette syndrome obsessive-compulsive disorde r ( O C D )
The therapy uses electrodes that are implanted into specific regions of the brain. The electrodes are powered by a pacemaker-like device placed in the upper chest area just underneath the skin. A wire running underneath the skin connects the device to the electrodes.
A doctor programs the device to generate the pulses it should deliver to the electrodes.
According to Dr. Jean-Philippe Langevin, a neurosurgeon and director of Restorative Neurosurgery and Deep Brain Stimulation Program for Pacific Neuroscience Institute at Providence Saint John’s Health Center in Santa Monica, CA, not involved in the research, the link between sleep and memory formation is an interesting phenomenon.
“There’s several neuroactivities that have been found in the brain that only happen while the patient is asleep and oftentimes tends to correlate with how good memory consolidation is happening,” he explained to Medical News Today.
“The general idea is that when you’re asleep, you don’t have to pay attention to any particular stimuli or anything in your environment, so it gives a chance for the brain to focus on memory consolidation. So if you’re during the day paying attention to something or you need your brain to focus on something to carry some function, then it may not be the best time to consolidate memories,” Dr. Langevin added. “Whereas at night, when things are quiet, then the brain can be used to generally consolidate some of the memories that happened during the day.”
– Dr. Jean-Philippe Langevin, neurosurgeon
Study co-author Prof. Yuval Nir, PhD, principal investigator in the Schools of Medicine, Neuroscience, and Biomedical Engineering at Tel Aviv University, told MNT that while sleep supporting long-term memory has been a scientific topic of great interest, existing research is either based on animal studies or noninvasive human studies.
For this study, Dr. Nir and his colleagues enlisted 18 people with epilepsy who already had electrodes implanted in their brains. The electrodes were being used to help identify where their seizures were coming from.
On the first night of the study, participants were shown photo pairings of animals with 25 easily-identifiable celebrities. They were immediately tested on their ability to recall the pairings before going to sleep. The participants’ recall abilities were also tested the next morning after having undisturbed sleep.
On the second and final night of the study, participants were shown 25 new animal and celebrity pairings. While they slept, scientists administered targeted deep-brain stimulation. And the participants were again tested on their memory of the pairings in the morning.
“We created a novel system that reads the electrical activity in and around the hippocampus during sleep in real-time and identifies specific times of activity to trigger stimulation pulses in the frontal lobe. Such stimulation helps create efficient communication between different brain regions responsible for creating new memories to those storing them for the long-term.”
– Prof. Yuval Nir, PhD, study coauthor
Upon analysis, the research team found study participants performed better on memory tests after the second night of undisturbed sleep with deep-brain stimulation, compared to the first night with just undisturbed sleep.
“Intervention during sleep represents a unique approach that can be further developed in the future to provide hope for people with memory impairments such as dementia,” Dr. Nir said.
“By boosting the natural process that happens during sleep, we were able to efficiently improve memory.”
Additionally, the scientists reported that key electrophysiological markers indicated that information moving between the hippocampus and cortex, giving them physical evidence of memory consolidation occurring.
“I think it’s really interesting that perhaps there’s a chance in the future that we can use neuromodulation to enhance memory in those patients who have (memory) deficits, whether it’s from dementia like Alzheimer’s disease, or even just traumatic (brain injury). The thought is that perhaps some of the regular mechanisms for memory formation and consolidation are damaged from the disease, but this could be a way to bypass some of the regular neural activity and then still get good memory function.”
– Dr. Jean-Philippe Langevin, neurosurgeon