biology

Rapid eye movement sleep

Rapid eye movement sleep is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Rapid eye movement sleep rather than just read about it. In short: Rapid eye movement sleep (REM sleep or REMS) is a unique phase of sleep in all mammals (including humans) and birds and in some reptiles, characterized by random rapid movement of the eyes, accompanied by low muscle tone throughout the body, and the propensity of the sleeper to dream vividly. The core body and brain temperatures increase during REM sleep and skin temperature decreases to the lowest values.

Key takeaways

Rapid eye movement sleep belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Rapid eye movement sleep to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Rapid eye movement sleep from memory before moving on to harder problems.

Reference excerpt

Rapid eye movement sleep (REM sleep or REMS) is a unique phase of sleep in all mammals (including humans) and birds and in some reptiles, characterized by random rapid movement of the eyes, accompanied by low muscle tone throughout the body, and the propensity of the sleeper to dream vividly. The core body and brain temperatures increase during REM sleep and skin temperature decreases to the lowest values. The REM phase is also known as paradoxical sleep (PS) and sometimes desynchronized sleep or dreamy sleep, because of physiological similarities to waking states including rapid, low-voltage desynchronized brain waves. Electrical and chemical activity regulating this phase seem to originate in the brain stem, and is characterized most notably by an abundance of the neurotransmitter acetylcholine, combined with a nearly complete absence of monoamine neurotransmitters histamine, serotonin and norepinephrine. Experiences of REM sleep are not transferred to permanent memory due to absence of norepinephrine. REM sleep is physiologically different from the other phases of sleep, which are collectively referred to as non-REM sleep (NREM sleep, NREMS, synchronized sleep). The absence of visual and auditory stimulation (sensory deprivation) during REM sleep can cause hallucinations. REM and non-REM sleep alternate within one sleep cycle, which lasts about 90 minutes in adult humans. As sleep cycles continue, they shift towards a higher proportion of REM sleep. The transition to REM sleep brings marked physical changes, beginning with electrical bursts called "ponto-geniculo-occipital waves" (PGO waves) originating in the brain stem. REM sleep occurs 4 times in a 7-hour sleep. Organisms in REM sleep suspend central homeostasis, allowing large fluctuations in respiration, thermoregulation and circulation which do not occur in any other modes of sleeping or waking. The body abruptly loses muscle tone, a state known as REM atonia. In 1953, Professor Nathaniel Kleitman and his student Eugene Aserinsky defined rapid eye movement and linked it to dreams. REM sleep was further described by researchers, including William Dement and Michel Jouvet. Many experiments have involved awakening test subjects whenever they begin to enter the REM phase, thereby producing a state known as REM deprivation. Subjects allowed to sleep normally again usually experience a modest REM rebound. Techniques of neurosurgery, chemical injection, electroencephalography, positron emission tomography, and reports of dreamers upon waking have all been used to study this phase of sleep.

Physiology

Electrical activity in the brain

REM sleep is called "paradoxical" because of its similarities to wakefulness. Although the body is paralyzed, the brain acts as if it is somewhat awake, with cerebral neurons firing with the same overall intensity as in wakefulness. Electroencephalography during REM sleep reveals fast, low amplitude, desynchronized neural oscillation (brainwaves) that resemble the pattern seen during wakefulness, which differ from the slow δ (delta) waves pattern of NREM deep sleep. An important element of this contrast is the 3–10 Hz theta rhythm in the hippocampus and 40–60 Hz gamma waves in the cortex; patterns of EEG activity similar to these rhythms are also observed during wakefulness. The cortical and thalamic neurons in the waking and REM sleeping brain are more depolarized (fire more readily) than in the NREM deep sleeping brain. Human theta wave activity predominates during REM sleep in both the hippocampus and the cortex. During REM sleep, electrical connectivity among different parts of the brain manifests differently than during wakefulness. Frontal and posterior areas are less coherent in most frequencies, a fact which has been cited in relation to the chaotic experience of dreaming. However, the posterior areas are more coherent with each other; as are the right and left hemispheres of the brain, especially during lucid dreams. Brain energy use in REM sleep, as measured by oxygen and glucose metabolism, equals or exceeds energy use in waking. The rate in non-REM sleep is 11–40% lower.

Brain stem Neural activity during REM sleep seems to originate in the brain stem, especially the pontine tegmentum and locus coeruleus. REM sleep is punctuated and immediately preceded by PGO (ponto-geniculo-occipital) waves, bursts of electrical activity originating in the brain stem. (PGO waves have long been measured directly in cats but not in humans because of constraints on experimentation; however, comparable effects have been observed in humans during "phasic" events which occur during REM sleep, and the existence of similar PGO waves is thus inferred.) These waves occur in clusters about every 6 seconds for 1–2 minutes during the transition from deep to paradoxical sleep. They exhibit their highest amplitude upon moving into the visual cortex and are a cause of the "rapid eye movements" in paradoxical sleep. Other muscles may also contract under the influence of these waves.

Forebrain Research in the 1990s using positron emission tomography (PET) confirmed the role of the brain stem and suggested that, within the forebrain, the limbic and paralimbic systems showed more activation than other areas. The areas activated during REM sleep are approximately inverse to those activated during non-REM sleep and display greater activity than in quiet waking. The "anterior paralimbic REM activation area" (APRA) includes areas linked with emotion, memory, fear and sex, and may thus relate to the experience of dreaming during REMS. More recent PET research has indicated that the distribution of brain activity during REM sleep varies in correspondence with the type of activity seen in the prior period of wakefulness. The superior frontal gyrus, medial frontal areas, intraparietal sulcus, and superior parietal cortex, areas involved in sophisticated mental activity, show equal activity in REM sleep as in wakefulness. The amygdala is also active during REM sleep and may participate in generating the PGO waves, and experimental suppression of the amygdala results in less REM sleep. The amygdala may also regulate cardiac function in lieu of the less active insular cortex.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Rapid eye movement sleep

Start with the simplest possible case. Write down what Rapid eye movement sleep claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Rapid eye movement sleep before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Rapid eye movement sleep ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Rapid eye movement sleep

In research: Rapid eye movement sleep appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Rapid eye movement sleep in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Rapid eye movement sleep is common in secondary-school and first-year university syllabi. It links to neighbouring topics Dreams, Neurophysiology, Sleep physiology, so understanding it makes those chapters shorter.
In everyday life: Look for Rapid eye movement sleep outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Rapid eye movement sleep in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Rapid eye movement sleep means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Rapid eye movement sleep out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Rapid eye movement sleep in simple terms?

Why does Rapid eye movement sleep matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Rapid eye movement sleep?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Rapid eye movement sleep.