Download Game Deep Sleep
Partenia Urtiaga
Sleep is important to a number of brain functions, including how nerve cells (neurons) communicate with each other. In fact, your brain and body stay remarkably active while you sleep. Recent findings suggest that sleep plays a housekeeping role that removes toxins in your brain that build up while you are awake.
Sleep is a complex and dynamic process that affects how you function in ways scientists are now beginning to understand. This booklet describes how your need for sleep is regulated and what happens in the brain during sleep.
The thalamus acts as a relay for information from the senses to the cerebral cortex (the covering of the brain that interprets and processes information from short- to long-term memory). During most stages of sleep, the thalamus becomes quiet, letting you tune out the external world. But during REM sleep, the thalamus is active, sending the cortex images, sounds, and other sensations that fill our dreams.
The basal forebrain, near the front and bottom of the brain, also promotes sleep and wakefulness, while part of the midbrain acts as an arousal system. Release of adenosine (a chemical by-product of cellular energy consumption) from cells in the basal forebrain and probably other regions supports your sleep drive. Caffeine counteracts sleepiness by blocking the actions of adenosine.
There are two basic types of sleep: rapid eye movement (REM) sleep and non-REM sleep (which has three different stages). Each is linked to specific brain waves and neuronal activity. You cycle through all stages of non-REM and REM sleep several times during a typical night, with increasingly longer, deeper REM periods occurring toward morning.
Stage 1 non-REM sleep is the changeover from wakefulness to sleep. During this short period (lasting several minutes) of relatively light sleep, your heartbeat, breathing, and eye movements slow, and your muscles relax with occasional twitches. Your brain waves begin to slow from their daytime wakefulness patterns.
Stage 2 non-REM sleep is a period of light sleep before you enter deeper sleep. Your heartbeat and breathing slow, and muscles relax even further. Your body temperature drops and eye movements stop. Brain wave activity slows but is marked by brief bursts of electrical activity. You spend more of your repeated sleep cycles in stage 2 sleep than in other sleep stages.
Stage 3 non-REM sleep is the period of deep sleep that you need to feel refreshed in the morning. It occurs in longer periods during the first half of the night. Your heartbeat and breathing slow to their lowest levels during sleep. Your muscles are relaxed and it may be difficult to awaken you. Brain waves become even slower.
REM sleep first occurs about 90 minutes after falling asleep. Your eyes move rapidly from side to side behind closed eyelids. Mixed frequency brain wave activity becomes closer to that seen in wakefulness. Your breathing becomes faster and irregular, and your heart rate and blood pressure increase to near waking levels. Most of your dreaming occurs during REM sleep, although some can also occur in non-REM sleep. Your arm and leg muscles become temporarily paralyzed, which prevents you from acting out your dreams. As you age, you sleep less of your time in REM sleep. Memory consolidation most likely requires both non-REM and REM sleep.
Sleep-wake homeostasis keeps track of your need for sleep. The homeostatic sleep drive reminds the body to sleep after a certain time and regulates sleep intensity. This sleep drive gets stronger every hour you are awake and causes you to sleep longer and more deeply after a period of sleep deprivation.
Factors that influence your sleep-wake needs include medical conditions, medications, stress, sleep environment, and what you eat and drink. Perhaps the greatest influence is the exposure to light. Specialized cells in the retinas of your eyes process light and tell the brain whether it is day or night and can advance or delay our sleep-wake cycle. Exposure to light can make it difficult to fall asleep and return to sleep when awakened.
Night shift workers often have trouble falling asleep when they go to bed, and also have trouble staying awake at work because their natural circadian rhythm and sleep-wake cycle is disrupted. In the case of jet lag, circadian rhythms become out of sync with the time of day when people fly to a different time zone, creating a mismatch between their internal clock and the actual clock.
Millions of people are using smartphone apps, bedside monitors, and wearable items (including bracelets, smart watches, and headbands) to informally collect and analyze data about their sleep. Smart technology can record sounds and movement during sleep, journal hours slept, and monitor heart beat and respiration. Using a companion app, data from some devices can be synced to a smartphone or tablet, or uploaded to a PC. Other apps and devices make white noise, produce light that stimulates melatonin production, and use gentle vibrations to help us sleep and wake.
Your health care provider may recommend a polysomnogram or other test to diagnose a sleep disorder. A polysomnogram typically involves spending the night at a sleep lab or sleep center. It records your breathing, oxygen levels, eye and limb movements, heart rate, and brain waves throughout the night. Your sleep is also video and audio recorded. The data can help a sleep specialist determine if you are reaching and proceeding properly through the various sleep stages. Results may be used to develop a treatment plan or determine if further tests are needed.
This study aimed to investigate the effects of pre-bedtime blue-light exposure on ratio of deep sleep and sleep quality. In this study, 11 healthy young men were exposed to three conditions for 1 h before bedtime: 1) incandescent light, 2) blue-light, or 3) blue light-blocking glasses on. The following morning, subjective sleep quality was measured using the Oguri-Shirakawa-Azumi Sleep Inventory. Sleep time, ratio of sleep, ratio of deep sleep, and body movements during sleep were measured using a mat sleep-scan (sleep scan, SL- 504; TANITA Corp., Japan) and an ambulatory portable sleep study system (LS-140; Fukuda Denshi Co. Ltd., Japan). Ratio of deep sleep was significantly decreased in the blue-light exposure group compared to the groups with incandescent light and blue light-blocking glasses (p < 0.01), There were no differences noted in sleep time or body movements among the three groups. These results suggest that blue-light exposure to affects sleep quality by reducing the ratio of deep sleep.
The research comes after decades of observations linking poor sleep to long-term problems with memory and thinking, Walker says. "We are now learning that there is a significant relationship between sleep and dementia, particularly Alzheimer's disease."
So Walker and a team of scientists set out to answer a question: "Can I look into your future and can I accurately estimate how much beta-amyloid you're going to accumulate over the next two years, the next four years, the next six years, simply on the basis of your sleep tonight?"
To find out, Walker's team studied 32 people in their 70s who had taken part in a sleep study that looked for the slow electrical waves that signal deep sleep. None of the participants had memory problems.
The scientists used brain scans to monitor levels of beta-amyloid in each participant for up to six years. And the results, published in the Nov. 2 issue of the journal Current Biology, showed people who got less deep had more beta-amyloid.
"So things like amyloid beta, which are implicated in Alzheimer's disease, seem to actually be removed more rapidly from the brain when an animal is asleep versus when they're awake," says Laura Lewis, an assistant professor of biomedical research at Boston University.
Ju was part of a study of people with obstructive sleep apnea, which repeatedly blocks the airway. These patients "seem to have a change in their ability to clear proteins or waste products from their brain," she says. "And people with sleep apnea are at higher risk for dementia down the line."
So Ju's team looked to see what happened after patients had been treated successfully for apnea. The scientists found that treatment resulted in more deep sleep and more beta-amyloid cleared from the brain.
Sleeping apps: Shows you all apps that are currently sleeping but may run in the background if you start to use them again. You can add apps to the list by tapping the + sign, selecting your desired app(s), and then tapping Add. To remove apps, tap More options (the three vertical dots), and then tap Remove apps. Select the app(s) you want to delete, and then tap Remove.
Deep sleeping apps: Shows you all apps that will never run in the background. They'll only work when you open them. You can add apps to the list by tapping the + sign, selecting your desired app(s), and then tapping Add. To remove apps, tap More options (the three vertical dots), and then tap Remove apps. Select the app(s) you want to delete, and then tap Remove.
Sleep stages are traditionally measured in a lab using an electroencephalogram to detect brain activity along with other systems to monitor eye and muscle activity. While this method is the gold standard for measuring sleep stages (source), your device can estimate your sleep stages in a more comfortable, convenient way.
Light sleep serves as the entry point into sleep each night as your body unwinds and slows down. This stage typically begins within minutes of falling asleep. During the early part of light sleep, you may drift between being awake and asleep. You may be somewhat alert and can be easily awoken. Breathing and heart rate typically decrease slightly during this stage.
760c119bf3