Rapid eye movement sleep

When you sleep, your eyes move fast.

This is a special time called REM sleep. During this time, you might have big dreams.

Your body stays very still. Your muscles stop working for a bit. This keeps you from moving while you dream.

Your brain stays very busy. It uses a lot of energy. It works almost as much as when you are awake.

Your body temperature can change too. You might feel warmer or cooler. This happens because your body does not stay the same.

This sleep happens many times each night. It helps your brain stay healthy. Do you remember your dreams?

Have you ever had a very vivid dream? This often happens during REM sleep. REM stands for rapid eye movement. This is a special phase of sleep for birds and mammals.

During this stage, your eyes move quickly and randomly. Your body also goes through a change called REM atonia. This means your muscles lose their tone and become still. This helps keep you from acting out your dreams.

Your brain stays very busy during this time. It uses as much power as it does when you are awake.

Scientists use a tool called an EEG to study brain waves. During REM, the brain shows fast waves that look like being awake. This is why some people call it paradoxical sleep.

Other parts of your body change too. Your heart rate and breathing can become irregular. Your body temperature might also go up or down.

This happens because the body stops its usual way of staying steady. In a normal seven-hour sleep, REM sleep occurs about four times. Each sleep cycle lasts about 90 minutes in adults.

Have you ever had a dream that felt so real you could almost touch it? This often happens during a special stage of sleep called REM sleep. REM stands for rapid eye movement. This phase is unique to birds and mammals, including humans.

During this time, your eyes move quickly and randomly behind your eyelids. Your body also enters a state called REM atonia. This is a type of temporary paralysis where your muscles lose their tone. This helps keep you still so you do not act out your dreams.

This stage is sometimes called paradoxical sleep. It gets this name because your brain looks very active, almost like you are awake. Scientists use a tool called an EEG to measure brain waves. During REM, the brain shows fast, low-voltage waves. These waves are very different from the slow waves seen in deep sleep.

In fact, your brain uses as much energy during REM as it does when you are awake. This high energy use comes from chemicals in the brain. A chemical called acetylcholine is very active during this phase. At the same time, other chemicals like serotonin are almost completely gone.

Researchers have worked for a long time to understand these cycles. In 1953, Professor Nathaniel Kleitman and his student Eugene Aserinsky first defined REM sleep. They were the ones who linked these eye movements to dreaming. Other scientists, such as William Dement and Michel Jouvet, helped describe it even more.

To study it, researchers use many tools. They might use neurosurgery or even special scans like PET scans. Some experiments involve waking people up right as they enter REM. This is called REM deprivation, and it can cause a "rebound" effect later.

There are many specific facts about how REM works in the body. In an adult human, one sleep cycle lasts about 90 minutes. During a typical seven-hour sleep, REM sleep occurs about four times. As the night goes on, you spend more time in REM. Your body also changes its way of staying steady, which is called homeostasis. During REM, your heart rate and breathing can become irregular. Your body temperature can also change. Your core temperature might rise while your skin temperature drops to its lowest values.

Understanding REM helps us see how our brain and body work together. It shows us that sleep is not just one long rest. Instead, it is a series of changing stages. For example, the brain stem sends out electrical bursts called PGO waves. These waves start in the brain stem and cause the rapid eye movements.

These cycles link our physical bodies to our inner worlds of dreams. Even though our muscles are still, our minds are traveling through vivid stories.

Rapid eye movement sleep, often called REM sleep, is a unique phase of sleep found in mammals and birds. It is characterized by random, rapid movements of the eyes and a state of low muscle tone throughout the body. This phase is also known as paradoxical sleep because the brain's activity looks very similar to being awake. During REM, the brain uses oxygen and glucose at a rate that equals or even exceeds its use during waking hours. In contrast, energy use during non-REM sleep is 11% to 40% lower.

The transition into REM sleep involves a complex sequence of biological events. It begins with electrical bursts called ponto-geniculo-occipital waves, or PGO waves. These waves originate in the brain stem and move toward the visual cortex. These bursts occur in clusters about every six seconds for one to two minutes during the transition. The PGO waves are a primary cause of the rapid eye movements observed during this stage. These eye movements are often shorter in duration than waking eye movements and tend to loop back to their starting point.

Chemical changes in the brain drive this unique state. REM sleep is characterized by an abundance of the neurotransmitter acetylcholine. This chemical is associated with faster brainwaves. At the same time, there is a nearly complete absence of monoamine neurotransmitters, specifically histamine, serotonin, and norepinephrine. The lack of norepinephrine is why experiences during REM are not transferred to permanent memory. Other chemicals, such as orexin and GABA, help regulate these transitions by inhibiting or promoting different sleep states.

Brain activity during REM sleep follows specific patterns. Electroencephalography, or EEG, shows fast, low-voltage, desynchronized neural oscillations. These patterns differ from the slow delta waves seen in deep non-REM sleep. Instead, the brain shows theta rhythms in the hippocampus and gamma waves in the cortex. These rhythms are very similar to the patterns seen when a person is awake. While the frontal and posterior areas of the brain are less coherent, which may contribute to chaotic dreams, the posterior areas remain more coherent with each other.

Historically, the discovery of this phase changed how we understand sleep. In 1953, Professor Nathaniel Kleitman and his student Eugene Aserinsky defined rapid eye movement and linked it to dreaming. Later, researchers like William Dement and Michel Jouvet provided further descriptions of the process. Scientists have used many tools to study REM, including neurosurgery, chemical injections, and positron emission tomography, or PET scans. One common experimental method is REM deprivation, where subjects are woken up whenever they enter the REM phase. When these subjects sleep normally again, they often experience a modest REM rebound.

REM sleep affects the entire body by suspending central homeostasis. Homeostasis is the process by which the body maintains a stable internal environment. During REM, the body experiences large fluctuations in respiration, circulation, and thermoregulation. Heart rate and breathing rates become irregular. The body also enters REM atonia, which is an almost complete paralysis caused by the inhibition of motor neurons. This prevents the sleeper from acting out their dreams. Additionally, the body's ability to regulate temperature is reduced. The core body temperature may increase, while skin temperature drops to its lowest values.

In adult humans, sleep occurs in cycles that last about 90 minutes. During a typical seven-hour sleep period, REM sleep occurs approximately four times. As the night progresses, the proportion of REM sleep within each cycle increases. This complex system shows how the brain stem and the forebrain work together to manage our internal states. The amygdala, an area linked to emotion, is active during REM and may even help regulate cardiac function. By studying these cycles, scientists continue to learn how our physical bodies and mental experiences are connected.