The neurobiology of sleep
Philip N. Murphy in The Routledge International Handbook of Psychobiology, 2018
The different sleep stages are organized into cycles, and so a sleeper will regularly switch from one stage to the next during a night of sleep. On average, a cycle lasts for around 90 minutes, although the sleep stage structure within each cycle changes as the night progresses; the first half of the night contains a high proportion of SWS and a few short episodes of REM sleep, whereas the second half contains less SWS and more REM sleep. However, around 50% of the total sleep time (TST; i.e., the time interval between sleep onset and final awakening) is spent in NREM-2 sleep. Figure 24.2 depicts a typical hypnogram (i.e., a representation of the changing stages during an episode of sleep), showing that the night is punctuated by several short periods of wakefulness. These usually last no more than a few minutes, and the sleeper does not remember them once he/she has fully woken up. Although these brief awakenings are normal, their overly frequent occurrence is a marker of poor sleep quality. Sleep architecture is influenced by several factors. For example, procedural learning during the day increases the time spent in REM sleep during the following night (Rauchs, Desgranges, Foret, & Eustache, 2005). Furthermore, some disorders, such as depression and post-traumatic stress disorder, are associated with disturbed sleep and specific alterations of the hypnogram. Lastly, as will be discussed below, the characteristics of sleep change over the life span.
Consciousness, Sleep and Hypnosis, Meditation, and Psychoactive Drugs
Mohamed Ahmed Abd El-Hay in Understanding Psychology for Medicine and Nursing, 2019
This phase of sleep is accompanied by considerable physiological arousal. Eyes move back and forth behind closed eyelids (the rapid eye movements), the heart rate, blood pressure, and respirations can fluctuate up and down. This phase is also known as paradoxical sleep, because while the brain and other body systems become more active, the muscles become more relaxed, which prevents the dreaming sleeper from acting out his or her dreams. Sexual arousal may occur in both sexes in this stage unrelated to dreams. Dreams usually occur during REM sleep. Stoppage of drugs that suppress REM sleep after prolonged intake lead to rebound symptoms, including vivid dreaming or even visual hallucinations. On average, we enter the REM stage approximately 90 minutes after falling asleep. The first cycle of REM sleep might last only 5–15 minutes, but each cycle becomes longer as sleep progress.
Audio Visual Entrainment and Acupressure Therapy for Insomnia
Anne George, Oluwatobi Samuel Oluwafemi, Blessy Joseph, Sabu Thomas, Sebastian Mathew, V. Raji in Holistic Healthcare, 2017
During stage 1, which is light sleep, one drifts in and out of sleep and can be awakened easily. The eyes move very slowly and muscle activity slows. People awakened from stage 1 sleep often remember fragmented visual images. Many also experience sudden muscle contractions called hypnic myoclonia, often preceded by a sensation of starting to fall. When entering stage 2 sleep, the eye movements stop and brain waves become slower, with occasional bursts of rapid waves called sleep spindles. In stage 3, extremely slow brain waves called delta waves begin to appear, interspersed with smaller, faster waves. By stage 4, the brain produces delta waves almost exclusively. It is very difficult to wake someone during stages 3 and 4, which together are called deep sleep. There is no eye movement or muscle activity. When the brain switches into REM sleep, the breathing becomes more rapid, irregular, and shallow, the eyes jerk rapidly in various directions, and the limb muscles become temporarily paralyzed. Heart rate and blood pressure are shown to increase. This is the stage of the sleep cycle in which dreams occur.
Update on nonpharmacological interventions in parasomnias
Published in Postgraduate Medicine, 2020
Maria Ntafouli, Andrea Galbiati, Mary Gazea, Claudio L.A. Bassetti, Panagiotis Bargiotas
Rapid Eye Movement (REM) sleep Behavior Disorder (RBD) is characterized by an abnormal behavior arising from REM sleep, which is accompanied by (oft frightening) vivid dreaming [58–60]. REM sleep phase is typically characterized by random, rapid movement of the eyes, REM atonia (low/missing muscle tone in the skeletal muscles), and the propensity of the sleeper to dream vividly. In RBD, REM atonia is disturbed, which in combination with vivid dreaming might lead the patient to ‘act out his/her dreams’ or dream enactment behavior (DEB), exhibiting a variety of motor activities. RBD affects less than 1% of the general adult population and 2–8% of the older adult population [61,62]. However, it can be commonly found in the context of neurodegenerative disorders such as Parkinson’s disease and dementia with Lewy body [63–66], predating their presentation by many years [67], but also in narcolepsy [68,69] and rarely also in the context of a parasomnia overlap disorder and its extreme form of a wake-sleep state breakdown (status dissociatus) [70–72]. Dreams can be violent in subjects with RBD and therefore, RBD represents a complex and potentially dangerous condition with increased risk of experiencing self-injurious behavior [73,74]. Types of injury ranged from light to severe, such as lacerations to fractures and subdural hematomas [75–79].
Assessing the impacts of ALAN and noise proxies on sleep duration and quality: evidence from a nation-wide survey in Israel
Published in Chronobiology International, 2021
Nahum M. Gabinet, Boris A. Portnov
Healthy sleep consists of two phases – rapid eye movement (REM) and non-rapid eye movement (NREM) (Carskadon and Dement 2005). Sleep begins with NREM, going through several stages into the REM sleep. The cycle between these stages continues throughout the night (Colten and Altevogt 2006). The length of the first NREM-REM cycle is ~70–90 min, while the later cycles are longer, lingering between 90 and 120 min per cycle, with brief episodes of wakefulness experienced, usually near the REM sleep transition (Carskadon and Dement 2005). As well established, drugs and medications influence REM sleep (Adrien 2002; Cheeta et al. 1997; Riemann et al. 2001), while drugs and alcohol may also induce nightmares (Colten and Altevogt 2006), phase-shift circadian rhythms (Carskadon and Dement 2005; Richardson 2005), insomnia (Thorpy 2012), and shorten life span (Siegel 2003).
Sleep paralysis in college students
Published in Journal of American College Health, 2022
Note from Researcher about Sleep Paralysis: Sleep paralysis is understood to be a disruption of the normal biological process that occurs during the transition between wake and sleep. When we are in a stage of sleep called REM (Rapid Eye Movement), our body is partially paralyzed. Sometimes this gets turned on too soon (as you're falling asleep) and sometimes it doesn't shut off quickly enough (as you're waking up). The hallucinations and altered body sensations are understood to be an instance where dreamlike experiences are melded with waking awareness (i.e., internal inputs are mixed with external inputs). This can obviously be a frightening experience for those who don't understand what is happening. This is a common experience for people who have a condition called narcolepsy-with-cataplexy, but it is not uncommon for people without that condition: approximately 28% of college students have experienced sleep paralysis at some point in their life.
Related Knowledge Centers
- Brainstem
- Eye
- Monoamine Neurotransmitter
- Neural Oscillation
- Sleep
- Muscle Tone
- Neurotransmitter
- Acetylcholine
- Dream
- NON-Rapid Eye Movement Sleep