The research is about sleep
How does sleep affect the brain? A study using the effect of listening to noise during sleep on Alzheimer’s disease, neurotoxins, and brain chemistry
There is no consensus as to why sleep is needed for survival. The consequences of not getting enough of this fundamental physical process is that you need to continue to seek answers.
The study showed that listening to pink noise during slow-wave sleep can have a stimulatory effect on parasympathetic activity, lowering cortisol levels in the morning, and slowing the heart rate. The cardiovascular system needs a break during sleep. “We know that if you don’t sleep well, your heart rate and blood pressure go up and you are at greater risk for cardiovascular disease,” Zee says.
In 2020, researchers found that hydra, a freshwater polyp with no brain, also enter a languid state at night11. These creatures need to rest a longer after being sleep deprived.
Nedergaard and colleagues reported that one benefit of sleep could be the removal of neurotoxins from the brain. The brain has a glymphatic system made of vessels that form a cell wall. In this tunnel, cerebrospinal fluid flows with interstitial fluid to remove proteins, including amyloid-β and tau, which are thought to have a role in Alzheimer’s disease.
“Sleep is the period where our brain doesn’t just rest, but it does all the housekeeping,” Nedergaard says. The glial cells that come in when the brain is quiet are the ones that clean the rest of the body. A function of the brain that is not compatible with wakefulness.
“What we showed is, every time the heart beats, you have the arteries expanding and moving the vessel wall and putting fluid into the brain,” she says. “It’s a very beautiful biological system.” When the mice were sleeping, the interstitial space grew by about 60 percent. This drastically increased the amount of exchange of cerebrospinal fluid and interstitial fluid as well as the rate of clearance of amyloid-β.
Brain overload can be solved by resetting to a critical point, which occurs mainly during sleep. The brain has a lot to do in the day such as learning, coordinating movement and recognizing faces. These tasks all change connections in the brain, essentially undermining the platform that is set up for that learning. Sleep, Hengen contends, allows the brain to reset. According to this hypothesis, the restoration, which occurs through a common biological process known as homeostasis, is the ‘set point’ at which the brain is able to maximize information-processing potential1.
“We asked them to remember word pairs during the day and then they slept,” says co-author Phyllis Zee, a neurologist and sleep-medicine specialist at the Feinberg School of Medicine in Chicago, Illinois. Those that had pink-noise stimulation did better on their memory tests than did those who listened to the control sounds.
Source: Sleep is essential — researchers are trying to work out why
Is Sleep Deprivation Important for the Development of Brain Development? Evidence from Fruit Flies and Mice on a Study by Rogulja
For decades, the main purpose of sleep was thought to be maintaining brain health. Babies and teenagers sleep for such long periods of time, according to this theory, because there is so much brain development going on at those stages.
In rats, most genes seem to be upregulated while the animals are awake and downregulated during sleep. Genes that are upregulated during periods of sleep deprivation are responsible for functions such as energy metabolism, hormone reception and protein synthesis5. The Brazilian researchers found that fruit flies that were sleep deprived have overexpression of genes that affect metabolism and levels of the hormone dopamine6.
The same thing happened to mice. When the animals were deprived of sleep, then allowed to sleep, they stopped expressing genes for fat absorption. Organelles called mitochondria sense this nutrient deficiency and signal cellular enzymes to make ROS to stimulate the proliferation of cells in the gut that are better at absorption, Rogulja says. After a day of restriction of sleep in mice, Rogulja could see that the animals were not getting enough energy from their bodies. Their bodies weren’t getting enough nutrition but they had fat in their guts after five days.
Source: Sleep is essential — researchers are trying to work out why
How a Light Bulb can Help a Home Heating System to Operate as a Heat Heat Heater: The Flies that Agree
“We looked at tissues all over the body,” Vaccaro says. We did not see anything when we looked at the brain. The one tissue that showed the most damage when the flies started to die was in the gut.”
After determining the ten-day timeline for sleep deprivation and death in flies, Vaccaro, who had previously studied sleep deprivation and ageing, began looking for markers of ageing in these insects. She and her colleagues found that the concentrations of reactive oxygen species (ROS) in the guts of flies were at their highest when the animals started dying. Small amounts of ROS are beneficial — they regulate the body’s immune response and help cells to defend against pathogens. These molecules accumulate to toxic levels if they don’t sleep.
Likewise, when the brain is further from its critical point, a person will feel more tired and need to fall asleep to reset. The closer the brain is to its critical point the more likely the person is to stay awake, because they will have plenty of capacity for doing and learning.
Hengen compares homeostasis to the familiar workings of a home heating system. A drop in a room’s temperature below the set point causes the heater to turn on, restoring the environment to the desired level of warmth.
This was like a light bulb that I’d been looking for. In terms of machine learning, “if you have a deep-learning network, and you continue to let it learn, it’ll exhibit catastrophic forgetting — the wheels come off and the thing stops. It just fails.”
Source: Sleep is essential — researchers are trying to work out why
Age and gender effects on the link between sleep and mortality in a multicentre study of the UK Biobank Sleep Heart Health Study (SHEHS)
What is the most important function of the brain? It might be tempting to say a specific task, such as communicating, finding food or avoiding predators. But none of these roles is possible if the brain’s cellular machinery isn’t functioning reliably. It is important to keep that reliability to the point that it might be the main purpose of sleep, according to a neuroscientist at Washington University.
“We started looking at lifespan and saw that the moment when sleep-deprived animals would start dying was pretty much always the same,” Rogulja says. They died within a week after they lost about 10% of their sleep each night. Those studies were in flies and mice — but the implications for other animals, including humans, was intriguing.
It would take years to answer these questions. But in six months, Rogulja’s postdoctoral assistant, Alexandra Vaccaro, found a tantalizing clue.
A study has found that exposure to too much light when we’re supposed to be asleep is linked to an increased risk of mental illness. Data from almost 87,000 people registered with the UK Biobank study were analysed, as well as data from Australia, the United States and the United Kingdom. They took a mental-health questionnaire online.
The greatest reduction in both prenatal and postpartum insomnia was seen in people who received therapist-assisted cognitive behavioural therapy for insomnia, which was delivered over the phone and by e-mail from the start of pregnancy through to three months after the birth. However, a mechanized ‘responsive bassinet’, which plays white noise and rocks back and forth when an infant cries, did not improve participants’ postpartum insomnia. The participants in the control condition received information about sleep hygiene.
Although napping is commonly viewed as the purview of the older person, the relationship between napping and disease or mortality risk is complicated by age. Researchers in China set out to investigate the effects of age and gender on this relationship, using data from about 3,000 participants who took part in a multicentre trial called the Sleep Heart Health Study.
A research team at the Duke-NUS Medical School in Singapore and the National University of Singapore said they thought that university students going to bed late were more likely to suffer from lower grades in early morning courses.
The study found that the amount of sleep that alcohol increased was offset by the decrease later on in the night. These changes, including a reduction in REM sleep, were evident across all three nights of drinking but most pronounced on the first night. That result suggested a growing tolerance to the effects of alcohol on sleep over multiple days.
One hour before lights out, 30 healthy adults aged 22 to 57 were given a drink that contained either a mixer or a mixer plus alcohol, which was designed to bring them to a blood alcohol level of 0.08 milligrams per litre — around four drinks for the average man. The participants were wired up to polysomnography machines to record their brain activity throughout the night. After three nights, the two groups were swapped over to the opposite drink type for a further three nights.
The results raise the prospect that the age-old practice of rocking someone to sleep could have clinical benefits in individuals with diseases that reduce sleep quality.
A group of flies was placed in the vibrating tubes for longer periods of time to see what effect the sleep they had on markers of Alzheimer’s disease. The researchers found that the flies that were vibrated to sleep slept better than the flies that weren’t and that the flies had less of the hallmarks of the disease.
