{"id":138,"date":"2020-04-29T14:23:41","date_gmt":"2020-04-29T14:23:41","guid":{"rendered":"https:\/\/digitaleditions.library.dal.ca\/intropsychneuro\/?post_type=chapter&#038;p=138"},"modified":"2022-09-01T13:46:04","modified_gmt":"2022-09-01T13:46:04","slug":"stages-of-sleep","status":"publish","type":"chapter","link":"https:\/\/digitaleditions.library.dal.ca\/intropsychneuro\/chapter\/stages-of-sleep\/","title":{"raw":"Stages of Sleep","rendered":"Stages of Sleep"},"content":{"raw":"<div class=\"PageContent-ny9bj0-0 iapMdy\">\r\n<div id=\"main-content\" class=\"MainContent__HideOutline-sc-6yy1if-0 bdVAq\">\r\n<div id=\"fea79b76-b417-40e2-8ab8-35161b0c4f3e\">\r\n<div id=\"26069\" class=\"ui-has-child-title\"><section>\r\n<div class=\"textbox textbox--learning-objectives\"><header class=\"textbox__header\">\r\n<p class=\"textbox__title\"><span style=\"color: #ffffff\">Learning Objectives<\/span><\/p>\r\n\r\n<\/header>\r\n<div class=\"textbox__content\">\r\n\r\nBy the end of this section, you will be able to:\r\n<ul>\r\n \t<li>Differentiate between REM and non-REM sleep<\/li>\r\n \t<li>Describe the differences between the three stages of non-REM sleep<\/li>\r\n \t<li>Understand the role that REM and non-REM sleep play in learning and memory<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n<\/section><\/div>\r\n<p id=\"fs-idp58109104\">Sleep is not a uniform state of being. Instead, sleep is composed of several different stages that can be differentiated from one another by the patterns of brain wave activity that occur during each stage. These changes in brain wave activity can be visualized using EEG and are distinguished from one another by both the frequency and amplitude of brain waves (<a class=\"autogenerated-content\" href=\"https:\/\/openstax.org\/books\/psychology-2e\/pages\/4-3-stages-of-sleep#Figure_04_03_SleepCycle\">Figure SC.7<\/a>). Sleep can be divided into two different general phases: REM sleep and non-REM (NREM) sleep.\u00a0<strong><span id=\"term242\">Rapid eye movement (REM)<\/span>\u00a0<\/strong>sleep is characterized by darting movements of the eyes under closed eyelids. Brain waves during REM sleep appear very similar to brain waves during wakefulness. In contrast,\u00a0<strong><span id=\"term243\">non-REM (NREM)<\/span><\/strong>\u00a0sleep is subdivided into three stages distinguished from each other and from wakefulness by characteristic patterns of brain waves. The first three stages of sleep are NREM sleep, while the fourth and final stage of sleep is REM sleep. In this section, we will discuss each of these stages of sleep and their associated patterns of brain wave activity.<\/p>\r\n\r\n<div id=\"Figure_04_03_SleepCycle\" class=\"os-figure\">\r\n<figure><span id=\"fs-idp1382544\"><img id=\"82656\" class=\"aligncenter\" src=\"https:\/\/openstax.org\/resources\/73ebb960c427c7e22230ff10bf9890d652be55d7\" alt=\"A photograph shows a person sleeping. Superimposed across the top of the picture is a line representing brainwave activity across the four stages of sleep. Above the line, from left to right, it reads stage 1, stage 2, stage 3, and stage 4. The wave amplitude is highest in late stage 2, and in the middle of stage 3 until stage 4. The wavelength is longer from late stage 2 through stage 3.\" \/><\/span><\/figure>\r\n<div class=\"os-caption-container\"><span class=\"os-title-label\">Figure SC<\/span><span class=\"os-number\">.7<\/span><span class=\"os-divider\">\u00a0<\/span><span class=\"os-caption\">Brainwave activity changes dramatically across the different stages of sleep. (credit \"sleeping\": modification of work by Ryan Vaarsi)<\/span><\/div>\r\n<\/div>\r\n<section id=\"fs-idm75903840\">\r\n<h3>NREM Stages of Sleep<\/h3>\r\n<p id=\"fs-idp58027264\">The first stage of NREM sleep is known as stage 1 sleep.<strong>\u00a0<span id=\"term244\">Stage 1 sleep<\/span><\/strong>\u00a0is a transitional phase that occurs between wakefulness and sleep, the period during which we drift off to sleep. During this time, there is a slowdown in both the rates of respiration and heartbeat. In addition, stage 1 sleep involves a marked decrease in both overall muscle tension and core body temperature.<\/p>\r\n<p id=\"fs-idp14745440\">In terms of brain wave activity, stage 1 sleep is associated with both alpha and theta waves. The early portion of stage 1 sleep produces\u00a0<strong><span id=\"term245\">alpha waves<\/span>,<\/strong> which are relatively low frequency (8\u201313Hz), high amplitude patterns of electrical activity (waves) that become synchronized (<a class=\"autogenerated-content\" href=\"https:\/\/openstax.org\/books\/psychology-2e\/pages\/4-3-stages-of-sleep#Figure_04_03_Stages\">Figure SC.8<\/a>). This pattern of brain wave activity resembles that of someone who is very relaxed, yet awake. As an individual continues through stage 1 sleep, there is an increase in theta wave activity.\u00a0<strong><span id=\"term246\">Theta waves<\/span><\/strong>\u00a0are even lower frequency (4\u20137 Hz), higher amplitude brain waves than alpha waves. It is relatively easy to wake someone from stage 1 sleep; in fact, people often report that they have not been asleep if they are awoken during stage 1 sleep.<\/p>\r\n\r\n<div id=\"Figure_04_03_Stages\" class=\"os-figure\">\r\n<figure>\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"649\"]<img id=\"44721\" src=\"https:\/\/openstax.org\/resources\/2df9bc486a589b76c3fff8367a4897bbc97c4709\" alt=\"A graph has a y-axis labeled \u201cEEG\u201d and an x-axis labeled \u201ctime (seconds.) Plotted along the y-axis and moving upward are the stages of sleep. First is REM, followed by Stage 3 NREM Delta, Stage 2 NREM Theta (sleep spindles; K-complexes), Stage 1 NREM Alpha, and Awake. Charted on the x axis is Time in seconds from 2\u201320 in 2 second intervals. Each sleep stage has associated wavelengths of varying amplitude and frequency. Relative to the others, \u201cawake\u201d has a very close wavelength and a medium amplitude. Stage 1 is characterized by a generally uniform wavelength and a relatively low amplitude which doubles and quickly reverts to normal every 2 seconds. Stage 2 is comprised of a similar wavelength as stage 1. It introduces the K-complex from seconds 10 through 12 which is a short burst of doubled or tripled amplitude and decreased wavelength. Stage 3 has a more uniform wave with gradually increasing amplitude. Finally, REM sleep looks much like stage 2 without the K-complex.\" width=\"649\" height=\"485\" \/> Figure SC.8\u00a0Brainwave activity changes dramatically across the different stages of sleep.[\/caption]<\/figure>\r\n<p class=\"os-caption-container\"><span style=\"text-align: initial;font-size: 1em\">As we move into<\/span><strong style=\"text-align: initial;font-size: 1em\">\u00a0<span id=\"term247\">stage 2 sleep<\/span><\/strong><span style=\"text-align: initial;font-size: 1em\">, the body goes into a state of deep relaxation. Theta waves still dominate the activity of the brain, but they are interrupted by brief bursts of activity known as sleep spindles (<\/span><a class=\"autogenerated-content\" style=\"text-align: initial;font-size: 1em\" href=\"https:\/\/openstax.org\/books\/psychology-2e\/pages\/4-3-stages-of-sleep#Figure_04_03_Stage2\">Figure SC.9<\/a><span style=\"text-align: initial;font-size: 1em\">). <\/span><strong style=\"text-align: initial;font-size: 1em\">A\u00a0<span id=\"term248\">sleep spindle<\/span><\/strong><span style=\"text-align: initial;font-size: 1em\">\u00a0is a rapid burst of higher frequency brain waves that may be important for learning and memory (Fogel &amp; Smith, 2011; Poe, Walsh, &amp; Bjorness, 2010). In addition, the appearance of K-complexes is often associated with stage 2 sleep. A\u00a0<\/span><strong style=\"text-align: initial;font-size: 1em\"><span id=\"term249\">K-complex<\/span><\/strong><span style=\"text-align: initial;font-size: 1em\">\u00a0is a very high amplitude pattern of brain activity that may in some cases occur in response to environmental stimuli. Thus, K-complexes might serve as a bridge to higher levels of arousal in response to what is going on in our environments (Hal\u00e1sz, 1993; Steriade &amp; Amzica, 1998).<\/span><\/p>\r\n\r\n<\/div>\r\n<div id=\"Figure_04_03_Stage2\" class=\"os-figure\">\r\n<figure>\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"487\"]<img id=\"71008\" src=\"https:\/\/openstax.org\/resources\/be62c72cc7c508782dbd58c526c48af8749ab353\" alt=\"A graph has an x-axis labeled \u201ctime\u201d and a y-axis labeled \u201cvoltage. A line illustrates brainwaves, with two areas labeled \u201csleep spindle\u201d and \u201ck-complex\u201d. The area labeled \u201csleep spindle\u201d has decreased wavelength and moderately increased amplitude, while the area labeled \u201ck-complex\u201d has significantly high amplitude and longer wavelength.\" width=\"487\" height=\"252\" \/> Figure SC.9\u00a0Stage 2 sleep is characterized by the appearance of both sleep spindles and K-complexes.[\/caption]<\/figure>\r\n<p class=\"os-caption-container\"><strong style=\"text-align: initial;font-size: 1em\"><span id=\"term250\">Stage 3<\/span><\/strong><span style=\"text-align: initial;font-size: 1em\">\u00a0is often referred to as deep sleep or slow-wave sleep because this stage is characterized by low frequency (less than 3 Hz), high amplitude\u00a0<\/span><strong style=\"text-align: initial;font-size: 1em\"><span id=\"term251\">delta waves<\/span><\/strong><span style=\"text-align: initial;font-size: 1em\">\u00a0(<\/span><a class=\"autogenerated-content\" style=\"text-align: initial;font-size: 1em\" href=\"https:\/\/openstax.org\/books\/psychology-2e\/pages\/4-3-stages-of-sleep#Figure_04_03_Deltawaves\">Figure SC.10<\/a><span style=\"text-align: initial;font-size: 1em\">). During this time, an individual\u2019s heart rate and respiration slow dramatically. It is much more difficult to awaken someone from sleep during stage 3 than during earlier stages. Interestingly, individuals who have increased levels of alpha brain wave activity (more often associated with wakefulness and transition into stage 1 sleep) during stage 3 often report that they do not feel refreshed upon waking, regardless of how long they slept (Stone, Taylor, McCrae, Kalsekar, &amp; Lichstein, 2008). It is worth noting that sometimes you may see slow-wave sleep divided into two stages, rather than just one. Previously, researchers distinguished between these two stages as being characterized by increased delta waves. However, it is now accepted as a single stage, Stage 3, known as slow-wave sleep.<\/span><\/p>\r\n\r\n<\/div>\r\n<div id=\"Figure_04_03_Deltawaves\" class=\"os-figure\">\r\n<figure>\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"975\"]<img id=\"23801\" src=\"https:\/\/openstax.org\/resources\/205a3775986ea2feb81f10357c8f5ec711fbab1e\" alt=\"Polysonograph a shows the pattern of delta waves, which are low frequency and high amplitude. Delta waves are found mostly in stage 3 of sleep. Chart b shows brainwaves at various stages of sleep, with stage 3 highlighted.\" width=\"975\" height=\"363\" \/> Figure SC.10\u00a0(a) Delta waves, which are low frequency and high amplitude, characterize (b) slow-wave stage 3 sleep.[\/caption]<\/figure>\r\n<h3 class=\"os-caption-container\"><span style=\"font-family: 'Cormorant Garamond', serif;font-size: 1em;font-weight: bold\">REM Sleep<\/span><\/h3>\r\n<\/div>\r\n<\/section><section id=\"fs-idm101227392\">\r\n<p id=\"fs-idm98619632\">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\u00a0<a class=\"autogenerated-content\" href=\"https:\/\/openstax.org\/books\/psychology-2e\/pages\/4-3-stages-of-sleep#Figure_04_03_REM\">Figure SC.11<\/a>, 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. Like NREM sleep, REM has been implicated in various aspects of learning and memory (Wagner, Gais, &amp; Born, 2001; Siegel, 2001).<\/p>\r\n\r\n<div id=\"Figure_04_03_REM\" class=\"os-figure\">\r\n<figure>\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"975\"]<img id=\"3634\" src=\"https:\/\/openstax.org\/resources\/417d7fe3801859d7456d4e52ce3ff985c1b4d5f5\" alt=\"Chart A is a polysonograph with the period of rapid eye movement (REM) highlighted. Chart b shows brainwaves at various stages of sleep, with the \u201cawake\u201d stage highlighted to show its similarity to the wave pattern of \u201cREM\u201d in chart A.\" width=\"975\" height=\"371\" \/> Figure SC.11\u00a0(a) 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 in (a), look very similar to those seen (b) during wakefulness.[\/caption]<\/figure>\r\n<\/div>\r\n<p id=\"fs-idm107552160\">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. In such instances, REM rebound may actually represent an adaptive response to stress in nondepressed individuals by suppressing the emotional salience of aversive events that occurred in wakefulness (Suchecki, Tiba, &amp; Machado, 2012). Sleep deprivation in general is associated with a number of negative consequences (Brown, 2012).<\/p>\r\n<p id=\"fs-idm181655808\">The hypnogram below (<a class=\"autogenerated-content\" href=\"https:\/\/openstax.org\/books\/psychology-2e\/pages\/4-3-stages-of-sleep#Figure_04_03_Hypnogram\">Figure SC.12<\/a>) shows a person\u2019s passage through the stages of sleep.<\/p>\r\n\r\n<div id=\"Figure_04_03_Hypnogram\" class=\"os-figure\">\r\n<figure>\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"649\"]<img id=\"89363\" src=\"https:\/\/openstax.org\/resources\/2dbbf4dfa4b03e90919100228b968f4dc7bcc678\" alt=\"This is a hypnogram showing the transitions of the sleep cycle during a typical eight hour period of sleep. During the first hour, the person goes through stages 1 and 2 and ends at 3. In the second hour, sleep oscillates in stage 3 before attaining a 30-minute period of REM sleep. The third hour follows the same pattern as the second, but ends with a brief awake period. The fourth hour follows a similar pattern as the third, with a slightly longer REM stage. In the fifth hour, stage 3 is no longer reached. The sleep stages are fluctuating from 2, to 1, to REM, to awake, and then they repeat with shortening intervals until the end of the eighth hour when the person awakens.\" width=\"649\" height=\"364\" \/> Figure SC.12\u00a0A hypnogram is a diagram of the stages of sleep as they occur during a period of sleep. This hypnogram illustrates how an individual moves through the various stages of sleep.[\/caption]<\/figure>\r\n<div class=\"os-caption-container\">\r\n<div class=\"textbox textbox--key-takeaways\"><header class=\"textbox__header\">\r\n<p class=\"textbox__title\"><span style=\"color: #ffffff\">LINK TO LEARNING<\/span><\/p>\r\n\r\n<\/header>\r\n<div class=\"textbox__content\"><span style=\"text-align: initial;font-size: 1em\">View this\u00a0<\/span><a style=\"text-align: initial;font-size: 1em\" href=\"http:\/\/openstax.org\/l\/sleepstages\" target=\"_blank\" rel=\"noopener nofollow\">video about the various stages of sleep<\/a><span style=\"text-align: initial;font-size: 1em\">\u00a0to learn more.<\/span><\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-idm4185024\" class=\"psychology link-to-learning ui-has-child-title\"><section><section id=\"fs-id1470001\"><strong style=\"text-align: initial;font-size: 1em\"><strong style=\"text-align: initial;font-size: 1em\"><a id=\"TTnatureofsleep\"><\/a>TRICKY TOPIC: RHYTHMIC NATURE OF SLEEP\r\n<\/strong><\/strong>[embed]https:\/\/youtu.be\/Oy3mKhQIeDk[\/embed]\r\n\r\n<\/section><section id=\"fs-id1470001\"><em><span id=\"term70\">If the video above does not load, click here:\u00a0<a href=\"https:\/\/youtu.be\/Oy3mKhQIeDk\">https:\/\/youtu.be\/Oy3mKhQIeDk<\/a>\r\nFor a full transcript of this video, click <a href=\"\/intropsychneuro\/back-matter\/appendix\/#natureofsleep\">here<\/a><\/span><\/em><\/section><section><strong>NOTE: In the image shown first at 4:32, slow-wave sleep is depicted as two separate stages (Stage 3 and 4), these two stages are now combined and referred to as Stage 3 only in this text.<\/strong><\/section><\/section><\/div>\r\n<section id=\"fs-idm89166016\">\r\n<h4>Dreams<\/h4>\r\n<p id=\"fs-idm31249056\">Dreams and their associated meanings vary across different cultures and periods of time. By the late 19th century, German psychiatrist Sigmund\u00a0<span id=\"term252\" class=\"no-emphasis\">Freud<\/span>\u00a0had become convinced that dreams represented an opportunity to gain access to the unconscious. By analyzing dreams, Freud thought people could increase self-awareness and gain valuable insight to help them deal with the problems they faced in their lives. Freud made distinctions between the manifest content and the latent content of dreams.\u00a0<strong><span id=\"term253\">Manifest content<\/span><\/strong>\u00a0is the actual content, or storyline, of a dream.\u00a0<span id=\"term254\"><strong>Latent conten<\/strong>t<\/span>, on the other hand, refers to the hidden meaning of a dream. For instance, if a woman dreams about being chased by a snake, Freud might have argued that this represents the woman\u2019s fear of sexual intimacy, with the snake serving as a symbol of a man\u2019s penis.<\/p>\r\n<p id=\"fs-idm29982832\">Freud was not the only theorist to focus on the content of dreams. The 20th century Swiss psychiatrist Carl Jung believed that dreams allowed us to tap into the collective unconscious. The\u00a0<strong><span id=\"term255\">collective unconscious<\/span><\/strong>, as described by\u00a0<span id=\"term256\" class=\"no-emphasis\">Jung<\/span>, is a theoretical repository of information he believed to be shared by everyone. According to Jung, certain symbols in dreams reflected universal archetypes with meanings that are similar for all people regardless of culture or location.<\/p>\r\n<p id=\"fs-idm29876928\">The sleep and dreaming researcher Rosalind Cartwright, however, believes that dreams simply reflect life events that are important to the dreamer. Unlike Freud and Jung, Cartwright\u2019s ideas about dreaming have found empirical support. For example, she and her colleagues published a study in which women going through divorce were asked several times over a five month period to report the degree to which their former spouses were on their minds. These same women were awakened during REM sleep in order to provide a detailed account of their dream content. There was a significant positive correlation between the degree to which women thought about their former spouses during waking hours and the number of times their former spouses appeared as characters in their dreams (Cartwright, Agargun, Kirkby, &amp; Friedman, 2006). Recent research (Horikawa, Tamaki, Miyawaki, &amp; Kamitani, 2013) has uncovered new techniques by which researchers may effectively detect and classify the visual images that occur during dreaming by using fMRI for neural measurement of brain activity patterns, opening the way for additional research in this area.<\/p>\r\n<p id=\"fs-idp61673568\">Alan Hobson, a neuroscientist, is credited for developing activation-synthesis theory of dreaming. Early versions of this theory proposed that dreams were not the meaning-filled representations of angst proposed by Freud and others, but were rather the result of our brain attempting to make sense of (\"synthesize\") the neural activity (\"activation\") that was happening during REM sleep. Recent adaptations (e.g., Hobson, 2002) continue to update the theory based on accumulating evidence. For example, Hobson (2009) suggests that dreaming may represent a state of protoconsciousness. In other words, dreaming involves constructing a virtual reality in our heads that we might use to help us during wakefulness. Among a variety of neurobiological evidence, John Hobson cites research on lucid dreams as an opportunity to better understand dreaming in general.\u00a0<span id=\"term257\">Lucid dreams<\/span>\u00a0are dreams in which certain aspects of wakefulness are maintained during a dream state. In a lucid dream, a person becomes aware of the fact that they are dreaming, and as such, they can control the dream\u2019s content (LaBerge, 1990).<\/p>\r\n\r\n<\/section><\/section><\/div>\r\n<\/div>\r\n<\/div>","rendered":"<div class=\"PageContent-ny9bj0-0 iapMdy\">\n<div id=\"main-content\" class=\"MainContent__HideOutline-sc-6yy1if-0 bdVAq\">\n<div id=\"fea79b76-b417-40e2-8ab8-35161b0c4f3e\">\n<div id=\"26069\" class=\"ui-has-child-title\">\n<section>\n<div class=\"textbox textbox--learning-objectives\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\"><span style=\"color: #ffffff\">Learning Objectives<\/span><\/p>\n<\/header>\n<div class=\"textbox__content\">\n<p>By the end of this section, you will be able to:<\/p>\n<ul>\n<li>Differentiate between REM and non-REM sleep<\/li>\n<li>Describe the differences between the three stages of non-REM sleep<\/li>\n<li>Understand the role that REM and non-REM sleep play in learning and memory<\/li>\n<\/ul>\n<\/div>\n<\/div>\n<\/section>\n<\/div>\n<p id=\"fs-idp58109104\">Sleep is not a uniform state of being. Instead, sleep is composed of several different stages that can be differentiated from one another by the patterns of brain wave activity that occur during each stage. These changes in brain wave activity can be visualized using EEG and are distinguished from one another by both the frequency and amplitude of brain waves (<a class=\"autogenerated-content\" href=\"https:\/\/openstax.org\/books\/psychology-2e\/pages\/4-3-stages-of-sleep#Figure_04_03_SleepCycle\">Figure SC.7<\/a>). Sleep can be divided into two different general phases: REM sleep and non-REM (NREM) sleep.\u00a0<strong><span id=\"term242\">Rapid eye movement (REM)<\/span>\u00a0<\/strong>sleep is characterized by darting movements of the eyes under closed eyelids. Brain waves during REM sleep appear very similar to brain waves during wakefulness. In contrast,\u00a0<strong><span id=\"term243\">non-REM (NREM)<\/span><\/strong>\u00a0sleep is subdivided into three stages distinguished from each other and from wakefulness by characteristic patterns of brain waves. The first three stages of sleep are NREM sleep, while the fourth and final stage of sleep is REM sleep. In this section, we will discuss each of these stages of sleep and their associated patterns of brain wave activity.<\/p>\n<div id=\"Figure_04_03_SleepCycle\" class=\"os-figure\">\n<figure><span id=\"fs-idp1382544\"><img decoding=\"async\" id=\"82656\" class=\"aligncenter\" src=\"https:\/\/openstax.org\/resources\/73ebb960c427c7e22230ff10bf9890d652be55d7\" alt=\"A photograph shows a person sleeping. Superimposed across the top of the picture is a line representing brainwave activity across the four stages of sleep. Above the line, from left to right, it reads stage 1, stage 2, stage 3, and stage 4. The wave amplitude is highest in late stage 2, and in the middle of stage 3 until stage 4. The wavelength is longer from late stage 2 through stage 3.\" \/><\/span><\/figure>\n<div class=\"os-caption-container\"><span class=\"os-title-label\">Figure SC<\/span><span class=\"os-number\">.7<\/span><span class=\"os-divider\">\u00a0<\/span><span class=\"os-caption\">Brainwave activity changes dramatically across the different stages of sleep. (credit &#8220;sleeping&#8221;: modification of work by Ryan Vaarsi)<\/span><\/div>\n<\/div>\n<section id=\"fs-idm75903840\">\n<h3>NREM Stages of Sleep<\/h3>\n<p id=\"fs-idp58027264\">The first stage of NREM sleep is known as stage 1 sleep.<strong>\u00a0<span id=\"term244\">Stage 1 sleep<\/span><\/strong>\u00a0is a transitional phase that occurs between wakefulness and sleep, the period during which we drift off to sleep. During this time, there is a slowdown in both the rates of respiration and heartbeat. In addition, stage 1 sleep involves a marked decrease in both overall muscle tension and core body temperature.<\/p>\n<p id=\"fs-idp14745440\">In terms of brain wave activity, stage 1 sleep is associated with both alpha and theta waves. The early portion of stage 1 sleep produces\u00a0<strong><span id=\"term245\">alpha waves<\/span>,<\/strong> which are relatively low frequency (8\u201313Hz), high amplitude patterns of electrical activity (waves) that become synchronized (<a class=\"autogenerated-content\" href=\"https:\/\/openstax.org\/books\/psychology-2e\/pages\/4-3-stages-of-sleep#Figure_04_03_Stages\">Figure SC.8<\/a>). This pattern of brain wave activity resembles that of someone who is very relaxed, yet awake. As an individual continues through stage 1 sleep, there is an increase in theta wave activity.\u00a0<strong><span id=\"term246\">Theta waves<\/span><\/strong>\u00a0are even lower frequency (4\u20137 Hz), higher amplitude brain waves than alpha waves. It is relatively easy to wake someone from stage 1 sleep; in fact, people often report that they have not been asleep if they are awoken during stage 1 sleep.<\/p>\n<div id=\"Figure_04_03_Stages\" class=\"os-figure\">\n<figure>\n<figure style=\"width: 649px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" id=\"44721\" src=\"https:\/\/openstax.org\/resources\/2df9bc486a589b76c3fff8367a4897bbc97c4709\" alt=\"A graph has a y-axis labeled \u201cEEG\u201d and an x-axis labeled \u201ctime (seconds.) Plotted along the y-axis and moving upward are the stages of sleep. First is REM, followed by Stage 3 NREM Delta, Stage 2 NREM Theta (sleep spindles; K-complexes), Stage 1 NREM Alpha, and Awake. Charted on the x axis is Time in seconds from 2\u201320 in 2 second intervals. Each sleep stage has associated wavelengths of varying amplitude and frequency. Relative to the others, \u201cawake\u201d has a very close wavelength and a medium amplitude. Stage 1 is characterized by a generally uniform wavelength and a relatively low amplitude which doubles and quickly reverts to normal every 2 seconds. Stage 2 is comprised of a similar wavelength as stage 1. It introduces the K-complex from seconds 10 through 12 which is a short burst of doubled or tripled amplitude and decreased wavelength. Stage 3 has a more uniform wave with gradually increasing amplitude. Finally, REM sleep looks much like stage 2 without the K-complex.\" width=\"649\" height=\"485\" \/><figcaption class=\"wp-caption-text\">Figure SC.8\u00a0Brainwave activity changes dramatically across the different stages of sleep.<\/figcaption><\/figure>\n<\/figure>\n<p class=\"os-caption-container\"><span style=\"text-align: initial;font-size: 1em\">As we move into<\/span><strong style=\"text-align: initial;font-size: 1em\">\u00a0<span id=\"term247\">stage 2 sleep<\/span><\/strong><span style=\"text-align: initial;font-size: 1em\">, the body goes into a state of deep relaxation. Theta waves still dominate the activity of the brain, but they are interrupted by brief bursts of activity known as sleep spindles (<\/span><a class=\"autogenerated-content\" style=\"text-align: initial;font-size: 1em\" href=\"https:\/\/openstax.org\/books\/psychology-2e\/pages\/4-3-stages-of-sleep#Figure_04_03_Stage2\">Figure SC.9<\/a><span style=\"text-align: initial;font-size: 1em\">). <\/span><strong style=\"text-align: initial;font-size: 1em\">A\u00a0<span id=\"term248\">sleep spindle<\/span><\/strong><span style=\"text-align: initial;font-size: 1em\">\u00a0is a rapid burst of higher frequency brain waves that may be important for learning and memory (Fogel &amp; Smith, 2011; Poe, Walsh, &amp; Bjorness, 2010). In addition, the appearance of K-complexes is often associated with stage 2 sleep. A\u00a0<\/span><strong style=\"text-align: initial;font-size: 1em\"><span id=\"term249\">K-complex<\/span><\/strong><span style=\"text-align: initial;font-size: 1em\">\u00a0is a very high amplitude pattern of brain activity that may in some cases occur in response to environmental stimuli. Thus, K-complexes might serve as a bridge to higher levels of arousal in response to what is going on in our environments (Hal\u00e1sz, 1993; Steriade &amp; Amzica, 1998).<\/span><\/p>\n<\/div>\n<div id=\"Figure_04_03_Stage2\" class=\"os-figure\">\n<figure>\n<figure style=\"width: 487px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" id=\"71008\" src=\"https:\/\/openstax.org\/resources\/be62c72cc7c508782dbd58c526c48af8749ab353\" alt=\"A graph has an x-axis labeled \u201ctime\u201d and a y-axis labeled \u201cvoltage. A line illustrates brainwaves, with two areas labeled \u201csleep spindle\u201d and \u201ck-complex\u201d. The area labeled \u201csleep spindle\u201d has decreased wavelength and moderately increased amplitude, while the area labeled \u201ck-complex\u201d has significantly high amplitude and longer wavelength.\" width=\"487\" height=\"252\" \/><figcaption class=\"wp-caption-text\">Figure SC.9\u00a0Stage 2 sleep is characterized by the appearance of both sleep spindles and K-complexes.<\/figcaption><\/figure>\n<\/figure>\n<p class=\"os-caption-container\"><strong style=\"text-align: initial;font-size: 1em\"><span id=\"term250\">Stage 3<\/span><\/strong><span style=\"text-align: initial;font-size: 1em\">\u00a0is often referred to as deep sleep or slow-wave sleep because this stage is characterized by low frequency (less than 3 Hz), high amplitude\u00a0<\/span><strong style=\"text-align: initial;font-size: 1em\"><span id=\"term251\">delta waves<\/span><\/strong><span style=\"text-align: initial;font-size: 1em\">\u00a0(<\/span><a class=\"autogenerated-content\" style=\"text-align: initial;font-size: 1em\" href=\"https:\/\/openstax.org\/books\/psychology-2e\/pages\/4-3-stages-of-sleep#Figure_04_03_Deltawaves\">Figure SC.10<\/a><span style=\"text-align: initial;font-size: 1em\">). During this time, an individual\u2019s heart rate and respiration slow dramatically. It is much more difficult to awaken someone from sleep during stage 3 than during earlier stages. Interestingly, individuals who have increased levels of alpha brain wave activity (more often associated with wakefulness and transition into stage 1 sleep) during stage 3 often report that they do not feel refreshed upon waking, regardless of how long they slept (Stone, Taylor, McCrae, Kalsekar, &amp; Lichstein, 2008). It is worth noting that sometimes you may see slow-wave sleep divided into two stages, rather than just one. Previously, researchers distinguished between these two stages as being characterized by increased delta waves. However, it is now accepted as a single stage, Stage 3, known as slow-wave sleep.<\/span><\/p>\n<\/div>\n<div id=\"Figure_04_03_Deltawaves\" class=\"os-figure\">\n<figure>\n<figure style=\"width: 975px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" id=\"23801\" src=\"https:\/\/openstax.org\/resources\/205a3775986ea2feb81f10357c8f5ec711fbab1e\" alt=\"Polysonograph a shows the pattern of delta waves, which are low frequency and high amplitude. Delta waves are found mostly in stage 3 of sleep. Chart b shows brainwaves at various stages of sleep, with stage 3 highlighted.\" width=\"975\" height=\"363\" \/><figcaption class=\"wp-caption-text\">Figure SC.10\u00a0(a) Delta waves, which are low frequency and high amplitude, characterize (b) slow-wave stage 3 sleep.<\/figcaption><\/figure>\n<\/figure>\n<h3 class=\"os-caption-container\"><span style=\"font-family: 'Cormorant Garamond', serif;font-size: 1em;font-weight: bold\">REM Sleep<\/span><\/h3>\n<\/div>\n<\/section>\n<section id=\"fs-idm101227392\">\n<p id=\"fs-idm98619632\">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\u00a0<a class=\"autogenerated-content\" href=\"https:\/\/openstax.org\/books\/psychology-2e\/pages\/4-3-stages-of-sleep#Figure_04_03_REM\">Figure SC.11<\/a>, 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. Like NREM sleep, REM has been implicated in various aspects of learning and memory (Wagner, Gais, &amp; Born, 2001; Siegel, 2001).<\/p>\n<div id=\"Figure_04_03_REM\" class=\"os-figure\">\n<figure>\n<figure style=\"width: 975px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" id=\"3634\" src=\"https:\/\/openstax.org\/resources\/417d7fe3801859d7456d4e52ce3ff985c1b4d5f5\" alt=\"Chart A is a polysonograph with the period of rapid eye movement (REM) highlighted. Chart b shows brainwaves at various stages of sleep, with the \u201cawake\u201d stage highlighted to show its similarity to the wave pattern of \u201cREM\u201d in chart A.\" width=\"975\" height=\"371\" \/><figcaption class=\"wp-caption-text\">Figure SC.11\u00a0(a) 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 in (a), look very similar to those seen (b) during wakefulness.<\/figcaption><\/figure>\n<\/figure>\n<\/div>\n<p id=\"fs-idm107552160\">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. In such instances, REM rebound may actually represent an adaptive response to stress in nondepressed individuals by suppressing the emotional salience of aversive events that occurred in wakefulness (Suchecki, Tiba, &amp; Machado, 2012). Sleep deprivation in general is associated with a number of negative consequences (Brown, 2012).<\/p>\n<p id=\"fs-idm181655808\">The hypnogram below (<a class=\"autogenerated-content\" href=\"https:\/\/openstax.org\/books\/psychology-2e\/pages\/4-3-stages-of-sleep#Figure_04_03_Hypnogram\">Figure SC.12<\/a>) shows a person\u2019s passage through the stages of sleep.<\/p>\n<div id=\"Figure_04_03_Hypnogram\" class=\"os-figure\">\n<figure>\n<figure style=\"width: 649px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" id=\"89363\" src=\"https:\/\/openstax.org\/resources\/2dbbf4dfa4b03e90919100228b968f4dc7bcc678\" alt=\"This is a hypnogram showing the transitions of the sleep cycle during a typical eight hour period of sleep. During the first hour, the person goes through stages 1 and 2 and ends at 3. In the second hour, sleep oscillates in stage 3 before attaining a 30-minute period of REM sleep. The third hour follows the same pattern as the second, but ends with a brief awake period. The fourth hour follows a similar pattern as the third, with a slightly longer REM stage. In the fifth hour, stage 3 is no longer reached. The sleep stages are fluctuating from 2, to 1, to REM, to awake, and then they repeat with shortening intervals until the end of the eighth hour when the person awakens.\" width=\"649\" height=\"364\" \/><figcaption class=\"wp-caption-text\">Figure SC.12\u00a0A hypnogram is a diagram of the stages of sleep as they occur during a period of sleep. This hypnogram illustrates how an individual moves through the various stages of sleep.<\/figcaption><\/figure>\n<\/figure>\n<div class=\"os-caption-container\">\n<div class=\"textbox textbox--key-takeaways\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\"><span style=\"color: #ffffff\">LINK TO LEARNING<\/span><\/p>\n<\/header>\n<div class=\"textbox__content\"><span style=\"text-align: initial;font-size: 1em\">View this\u00a0<\/span><a style=\"text-align: initial;font-size: 1em\" href=\"http:\/\/openstax.org\/l\/sleepstages\" target=\"_blank\" rel=\"noopener nofollow\">video about the various stages of sleep<\/a><span style=\"text-align: initial;font-size: 1em\">\u00a0to learn more.<\/span><\/div>\n<\/div>\n<\/div>\n<\/div>\n<div id=\"fs-idm4185024\" class=\"psychology link-to-learning ui-has-child-title\">\n<section>\n<section id=\"fs-id1470001\"><strong style=\"text-align: initial;font-size: 1em\"><strong style=\"text-align: initial;font-size: 1em\"><a id=\"TTnatureofsleep\"><\/a>TRICKY TOPIC: RHYTHMIC NATURE OF SLEEP<br \/>\n<\/strong><\/strong><iframe loading=\"lazy\" id=\"oembed-1\" title=\"Tricky Topics: Rhythmic Nature of Sleep\" width=\"500\" height=\"281\" src=\"https:\/\/www.youtube.com\/embed\/Oy3mKhQIeDk?feature=oembed&#38;rel=0\" frameborder=\"0\" allowfullscreen=\"allowfullscreen\"><\/iframe><\/p>\n<\/section>\n<section><em><span id=\"term70\">If the video above does not load, click here:\u00a0<a href=\"https:\/\/youtu.be\/Oy3mKhQIeDk\">https:\/\/youtu.be\/Oy3mKhQIeDk<\/a><br \/>\nFor a full transcript of this video, click <a href=\"\/intropsychneuro\/back-matter\/appendix\/#natureofsleep\">here<\/a><\/span><\/em><\/section>\n<section><strong>NOTE: In the image shown first at 4:32, slow-wave sleep is depicted as two separate stages (Stage 3 and 4), these two stages are now combined and referred to as Stage 3 only in this text.<\/strong><\/section>\n<\/section>\n<\/div>\n<section id=\"fs-idm89166016\">\n<h4>Dreams<\/h4>\n<p id=\"fs-idm31249056\">Dreams and their associated meanings vary across different cultures and periods of time. By the late 19th century, German psychiatrist Sigmund\u00a0<span id=\"term252\" class=\"no-emphasis\">Freud<\/span>\u00a0had become convinced that dreams represented an opportunity to gain access to the unconscious. By analyzing dreams, Freud thought people could increase self-awareness and gain valuable insight to help them deal with the problems they faced in their lives. Freud made distinctions between the manifest content and the latent content of dreams.\u00a0<strong><span id=\"term253\">Manifest content<\/span><\/strong>\u00a0is the actual content, or storyline, of a dream.\u00a0<span id=\"term254\"><strong>Latent conten<\/strong>t<\/span>, on the other hand, refers to the hidden meaning of a dream. For instance, if a woman dreams about being chased by a snake, Freud might have argued that this represents the woman\u2019s fear of sexual intimacy, with the snake serving as a symbol of a man\u2019s penis.<\/p>\n<p id=\"fs-idm29982832\">Freud was not the only theorist to focus on the content of dreams. The 20th century Swiss psychiatrist Carl Jung believed that dreams allowed us to tap into the collective unconscious. The\u00a0<strong><span id=\"term255\">collective unconscious<\/span><\/strong>, as described by\u00a0<span id=\"term256\" class=\"no-emphasis\">Jung<\/span>, is a theoretical repository of information he believed to be shared by everyone. According to Jung, certain symbols in dreams reflected universal archetypes with meanings that are similar for all people regardless of culture or location.<\/p>\n<p id=\"fs-idm29876928\">The sleep and dreaming researcher Rosalind Cartwright, however, believes that dreams simply reflect life events that are important to the dreamer. Unlike Freud and Jung, Cartwright\u2019s ideas about dreaming have found empirical support. For example, she and her colleagues published a study in which women going through divorce were asked several times over a five month period to report the degree to which their former spouses were on their minds. These same women were awakened during REM sleep in order to provide a detailed account of their dream content. There was a significant positive correlation between the degree to which women thought about their former spouses during waking hours and the number of times their former spouses appeared as characters in their dreams (Cartwright, Agargun, Kirkby, &amp; Friedman, 2006). Recent research (Horikawa, Tamaki, Miyawaki, &amp; Kamitani, 2013) has uncovered new techniques by which researchers may effectively detect and classify the visual images that occur during dreaming by using fMRI for neural measurement of brain activity patterns, opening the way for additional research in this area.<\/p>\n<p id=\"fs-idp61673568\">Alan Hobson, a neuroscientist, is credited for developing activation-synthesis theory of dreaming. Early versions of this theory proposed that dreams were not the meaning-filled representations of angst proposed by Freud and others, but were rather the result of our brain attempting to make sense of (&#8220;synthesize&#8221;) the neural activity (&#8220;activation&#8221;) that was happening during REM sleep. Recent adaptations (e.g., Hobson, 2002) continue to update the theory based on accumulating evidence. For example, Hobson (2009) suggests that dreaming may represent a state of protoconsciousness. In other words, dreaming involves constructing a virtual reality in our heads that we might use to help us during wakefulness. Among a variety of neurobiological evidence, John Hobson cites research on lucid dreams as an opportunity to better understand dreaming in general.\u00a0<span id=\"term257\">Lucid dreams<\/span>\u00a0are dreams in which certain aspects of wakefulness are maintained during a dream state. In a lucid dream, a person becomes aware of the fact that they are dreaming, and as such, they can control the dream\u2019s content (LaBerge, 1990).<\/p>\n<\/section>\n<\/section>\n<\/div>\n<\/div>\n<\/div>\n","protected":false},"author":13,"menu_order":4,"template":"","meta":{"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"part":25,"_links":{"self":[{"href":"https:\/\/digitaleditions.library.dal.ca\/intropsychneuro\/wp-json\/pressbooks\/v2\/chapters\/138"}],"collection":[{"href":"https:\/\/digitaleditions.library.dal.ca\/intropsychneuro\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/digitaleditions.library.dal.ca\/intropsychneuro\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/digitaleditions.library.dal.ca\/intropsychneuro\/wp-json\/wp\/v2\/users\/13"}],"version-history":[{"count":19,"href":"https:\/\/digitaleditions.library.dal.ca\/intropsychneuro\/wp-json\/pressbooks\/v2\/chapters\/138\/revisions"}],"predecessor-version":[{"id":2320,"href":"https:\/\/digitaleditions.library.dal.ca\/intropsychneuro\/wp-json\/pressbooks\/v2\/chapters\/138\/revisions\/2320"}],"part":[{"href":"https:\/\/digitaleditions.library.dal.ca\/intropsychneuro\/wp-json\/pressbooks\/v2\/parts\/25"}],"metadata":[{"href":"https:\/\/digitaleditions.library.dal.ca\/intropsychneuro\/wp-json\/pressbooks\/v2\/chapters\/138\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/digitaleditions.library.dal.ca\/intropsychneuro\/wp-json\/wp\/v2\/media?parent=138"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/digitaleditions.library.dal.ca\/intropsychneuro\/wp-json\/pressbooks\/v2\/chapter-type?post=138"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/digitaleditions.library.dal.ca\/intropsychneuro\/wp-json\/wp\/v2\/contributor?post=138"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/digitaleditions.library.dal.ca\/intropsychneuro\/wp-json\/wp\/v2\/license?post=138"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}