It is much more difficult to awaken someone from sleep during stage 3 than during earlier stages. Figure 4. Delta waves, which are low frequency and high amplitude, characterize slow-wave stage 3 sleep.

As mentioned earlier, REM sleep is marked by rapid movements of the eyes. The brain waves associated with this stage of sleep are very similar to those observed when a person is awake, as shown in Figure 5, and this is the period of sleep in which dreaming occurs.

It is also associated with paralysis of muscle systems in the body with the exception of those that make circulation and respiration possible. Therefore, no movement of voluntary muscles occurs during REM sleep in a normal individual; REM sleep is often referred to as paradoxical sleep because of this combination of high brain activity and lack of muscle tone.

Figure 5. A period of rapid eye movement is marked by the short red line segment. The brain waves associated with REM sleep, outlined in the red box, look very similar to those seen during wakefulness.

If people are deprived of REM sleep and then allowed to sleep without disturbance, they will spend more time in REM sleep in what would appear to be an effort to recoup the lost time in REM.

This is known as the REM rebound , and it suggests that REM sleep is also homeostatically regulated. Aside from the role that REM sleep may play in processes related to learning and memory, REM sleep may also be involved in emotional processing and regulation.

Sleep deprivation in general is associated with a number of negative consequences Brown, Figure 6. This hypnogram illustrates how an individual moves through the various stages of sleep.

Deeper NREM sleep occurs early on in the night, while the duration of REM sleep increases as the night progresses. Researchers believe that one important function of sleep is to facilitate learning and memory. How does knowing this help you in your college studies?

What changes could you make to your study and sleep habits to maximize your mastery of the material covered in class? Improve this page Learn More. Skip to main content. States of Consciousness. Search for:.

Stages of Sleep Learning Objectives Differentiate between REM and non-REM sleep Describe the stages of sleep. Try It. Think It Over Researchers believe that one important function of sleep is to facilitate learning and memory. Glossary alpha wave: type of relatively low frequency, relatively high amplitude brain wave that becomes synchronized; characteristic of the beginning of stage 1 sleep.

delta wave: type of low frequency, high amplitude brain wave characteristic of stage 3 sleep. K-complex: very high amplitude pattern of brain activity associated with stage 2 sleep that may occur in response to environmental stimuli.

non-REM NREM : period of sleep outside periods of rapid eye movement REM sleep. rapid eye movement REM sleep: period of sleep characterized by brain waves very similar to those during wakefulness and by darting movements of the eyes under closed eyelids.

sleep spindle: rapid burst of high frequency brain waves during stage 2 sleep that may be important for learning and memory. stage 1 sleep: first stage of sleep; transitional phase that occurs between wakefulness and sleep; the period during which a person drifts off to sleep.

The first stage of the sleep cycle is a transition period between wakefulness and sleep. If you awaken someone during this stage, they might report that they were not asleep. During stage 1 sleep:. This brief period of sleep lasts for around five to 10 minutes.

People spend about half of their total sleep time during NREM stage 2, which lasts for about 20 minutes per cycle. During stage 2 sleep:. The brain also begins to produce bursts of rapid, rhythmic brain wave activity, which are known as sleep spindles.

They are thought to be a feature of memory consolidation—when your brain gathers, processes, and filters new memories you acquired the previous day. While this is occurring, your body slows down in preparation for NREM stage 3 sleep and REM sleep—the deep sleep stages when the brain and body repair, restore, and reset for the coming day.

Deep, slow brain waves known as delta waves begin to emerge during NREM stage 3 sleep—a stage that is also referred to as delta sleep. This is a period of deep sleep where any environmental noises or activity may fail to wake the sleeping person.

Sleepwalking typically occurs during NREM stage 3 sleep. Children and young adults are more likely to sleepwalk than older adults. During NREM stage 3 sleep:. During this deep sleep stage, your body starts its physical repairs. Getting enough NREM stage 3 sleep makes you feel refreshed the next day.

Meanwhile, your brain consolidates declarative memories—for example, general knowledge, facts or statistics, personal experiences, and other things you have learned. While your brain is aroused with mental activities during REM sleep, the fourth stage of sleep, your voluntary muscles become immobilized.

However, your body is temporarily paralyzed—a good thing, as it prevents you from acting out your dreams. REM sleep begins approximately 90 minutes after falling asleep.

At this time:. Like stage 3, memory consolidation also happens during REM sleep. However, it is thought that REM sleep is when emotions and emotional memories are processed and stored. Your brain also uses this time to cement information into memory, making it an important stage for learning.

During deep sleep stage 3 and REM , your cells repair and rebuild, and hormones are secreted to promote bone and muscle growth.

Your body also uses deep sleep to strengthen your immunity so you can fight off illness and infection. When you have a full night of uninterrupted sleep, the stages progress as follows:. Once REM sleep is over, the body usually returns to NREM stage 2 before beginning the cycle.

Time spent in each stage changes throughout the night as the cycle repeats about four to five times total. Sleep architecture refers to the cycles and stages a person experiences at night.

According to the National Sleep Foundation, a full sleep cycle is generally around 90 minutes long. Any time you have trouble falling asleep or staying asleep at night, your sleep cycle will be affected.

Interrupted sleep is the term used to describe sleep that is not continuous throughout the night. When this happens, your sleep cycle can be disrupted. An in-progress sleep stage may be cut short, and a cycle may repeat before finishing. Several issues can interrupt your sleep cycles. This may happen occasionally or chronically, depending on which one is at play.

Some factors that are associated with interrupted sleep and, therefore, may affect your sleep stages include:. Not spending enough time in each sleep stage or properly cycling through the stages of sleep can affect you in various ways, potentially having short-term and long-term consequences.

A few examples of issues that can arise from a disrupted sleep cycle include problems with:. People with a disrupted sleep cycle are also at greater risk for:.

According to the Centers for Disease Control and Prevention, 1 in 3 adults in the US reports not getting enough sleep. There are things everyone can try to help improve the quality and quantity of sleep. If you practice good sleep hygiene , you can often improve the quantity and quality of your sleep.

If you still are not getting sufficient sleep after trying the above tips for at least a week, see a healthcare professional to assess if you need other assistance, such as medication or a sleep apnea device. As your body progresses through the four sleep cycle stages—stages 1 through 3 non-rapid eye movement, or NREM and stage 4 rapid eye movement, or REM , it transitions through different biological processes that affect your temperature, breathing, cells, and muscles.

All the while, your brain is busy forming, organizing, and storing memories. The sleep cycle follows a specific pattern, but that can be interrupted because of various habits, health conditions, and even older age.

Over time, not getting enough sleep and not cycling through the four stages can cause physical and mental health issues. The American Academy of Sleep Medicine and the Sleep Research Society recommend that adults get seven or more hours of sleep per night.

If you experience any of the following, make an appointment to see a healthcare provider, as you may not be getting the sleep you need:.

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Quantifying sleep architecture dynamics and individual differences using big data and Bayesian networks. PLoS One. Feld GB , Diekelmann S. Sleep smart—optimizing sleep for declarative learning and memory.

Front Psychol. National Library of Medicine: MedlinePlus. Glosemeyer RW, Diekelmann S, Cassel W, et al. Selective suppression of rapid eye movement sleep increases next-day negative affect and amygdala responses to social exclusion.

Sci Rep. Johns Hopkins Medicine. The science of sleep: understanding what happens when you sleep.