Brain noise contains the unique features of dream sleep

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When we dream, our brain is filled with noisy electrical activity that looks much like that of the waking brain.

But researchers at the University of California, Berkeley can pull signals from the dream, the noise that uniquely defines REM sleep, to help monitor sleep-impaired and unconscious coma patients and those under anesthesia. There is a possibility.

Every year, hundreds of thousands of people undergo overnight studies to diagnose sleep problems, most of which connect to the electroencephalogram (EEG) and shift from wakefulness to deep-wave slow-wave sleep I am monitoring the brain activity when I go to sleep. However, EEG alone does not tell if the patient is awake or dreaming. Doctors need to record rapid eye movements, or names and muscle tensions, to distinguish REM sleep. dream.

“There really is now a metric that accurately conveys REM sleep. It’s an unconscious, universal metric,” says professor of psychology and neuroscience at the University of California, Berkeley, July in an online journal. Robert Knight, the first author of a paper describing the study published on 28th, said: eLife..

Matthew Walker, a co-author and sleep researcher who is a professor of psychology and neuroscience at the University of California, Berkeley, said: “And when we first measure that simple electrical feature, we can accurately and accurately determine the state of consciousness that someone is experiencing.

The ability to distinguish REM sleep by EEG allows doctors to monitor anesthetized people during anesthesia to investigate how the unconsciousness caused by narcotics differs from normal sleep. That is the main reason why an anesthetist, first author Janna Lendner, started her research.

“We often tell patients that you’re going to sleep now, and I wanted to know how much these two conditions really overlap,” said the Department of Anesthesiology at the University of Medicine. Her fourth year at Residency, UC Berkeley Postdoctoral Research Center, Lendner Center in Tubingen, Germany. “There are some side effects of anesthesia. A little learning about how they overlap may allow anesthesia to hijack the sleep pathway. It may improve anesthesia in the long run. “

Sleep calms the brain

As Walker wrote in his 2017 book Why We Sleep, sleep enriches a variety of functions, such as learning, memory, and the ability to make logical decisions and choices. Serving our psychological well-being compassionately, sleep realigns emotional brain circuits, allowing us to calmly calm and navigate the social and psychological tasks of the next day. “

Brain activity recorded by three frontal scalp EEG electrodes during sleep night. The white time-resolved spectral slope tracks fundamental changes in alertness levels. (Image by Janna Lendner et al., CC BY 4.0)

Sleep disorders interfere with all of this and increase the risk of medical, psychiatric and neurological disorders.

Most sleep studies focus on the synchronized rhythmic waves that flow through neural networks in the brain, usually from the slow waves that represent late-night sleep to the first few hours of night. These waves pop above many common activities, also called 1/f, and are usually ignored as noise and are ignored.

But Knight and his lab have been seeing this “noise” for ten years and have found it to contain useful information about the state of the brain. For example, in 2015, he and Bradley Voytek, a former PhD student currently enrolled in UC San Diego, discovered that the amount of radiofrequency activity increased with age. Lendner found that a faster decline in high frequency activity compared to low frequency activity was a unique feature of REM sleep.

“This background activity isn’t rhythmic, it’s been overlooked for quite some time,” said Lendner. “Although it is sometimes called noise, it is not noise. It also contains a lot of information about the underlying wakefulness level. This measurement allows us to distinguish between REM sleep and wakefulness by looking only at the EEG. I can.”

Janna Lendner from OR. (Photo courtesy of Janna Lendner)

Slow waves are associated with suppression of activity in the brain, whereas high-frequency activity, such as that seen during waking, is associated with excitatory behavior, so a sharp decrease is associated with many activities in the brain, including associated activity. Activity muscle movement is tamped during REM sleep.

The new measurement quantifies the relationship between brain activity at various frequencies (activity at frequencies of about 1 cycle per second to 50 cycles per second) to determine the rate of decline of the slope, or spectrum. This 1/f “drop-off” is sharper in REM sleep than when awake or under anesthesia.

Lendner puts the electrodes in the brain to look for the cause of epilepsy as a prologue to the need for 20 brain operations at night, recorded via electroencephalographic scalp electrodes in a sleep laboratory at the University of California, Berkeley, Walker. We found this characteristic measure in 10 people who were placed to relieve seizures.

She also recorded brain activity in 12 epilepsy patients and 9 other patients who underwent spinal surgery on general anesthesia propofol.

Lendner is currently examining the brain records of comatose patients to see how their brain activity changes over the course of the day, and using 1/f drop-off the likelihood of emergence from coma I’m checking if I can show you.

“More importantly, I think it’s another indicator for assessing coma,” Knight said. “1/f is very sensitive. For example, you can solve if someone is in a minimal state of consciousness, they are not moving, and if they are more alert than you think.”

This study was funded by the German Research Foundation (Deutsche Forschungsgemeinschaft), the National Institute of Neurological Disorders and Stroke, and the National Institute of Mental Health. Other co-authors eLife Thesis is Randolph Helfrich of the Tubingen University Medical Center, Bryce Mander and Jack Linn from the University of California Irvine, and Lewis Ron Mustard and Parlarson of the University of Oslo Medical Center. Knight, Walker, and Lendner are members of the Helenvirus Neuroscience Institute at the University of California, Berkeley.

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