Chinese, Mandarin

Spanish

English

Hindi

Arabic

Portuguese

Bengali

Russian

Japanese

Punjabi

German

Javanese

Malay

Telugu

Vietnamese

Korean

French

Marathi

Tamil

Urdu

Turkish

Italian

Chinese, Yue / Cantonese

Thai

Gujarati

Chinese, Jin

Chinese, Min Nan

Persian, Dari

Persian, Western

Polish

Pashto

Kannada

Chinese, Xiang

Malayalam

Sundanese

Hausa

Odia

Burmese

Chinese, Hakka

Ukrainian

Bihari, Bhojpuri

Tagalog

Yoruba

Bihari, Maithili

Uzbek

Sindhi

Amharic

Fula

Romanian

Oromo

Igbo

Azerbaijani

Chinese, Gan

Dutch

Kurdish, Central

Kurdish, Northern

Kurdish, Southern

Malagasy

Lahnda, Saraiki

Nepali

Sinhalese

Chittagonian

Zhuang

Khmer

Turkmen

Assamese

Madurese

Somali

Marwari

Bihari, Magahi

Haryanvi

Hungarian

Chhattisgarhi

Greek, Modern

Chewa

Dakhini

Akan, Twi

Akan, Fante

Kazakh

Chinese, Min Bei

Sylheti

Zulu

Czech

Kinyarwanda

Marwari, Dhundhari

Haitian Creole

Chinese, Min Dong

Ilocano

Quechua

Kirundi

Swedish

Hmong

Shona

Uyghur

Hiligaynon

Mossi

Xhosa

Belarusian

Balochi

Psychology

<OpenstaxParagraph>
	By the end of this section, you will be able to:
</OpenstaxParagraph>
<OpenstaxUl>
	<OpenstaxLi>
		Differentiate between REM and non-REM sleep
	</OpenstaxLi>
	<OpenstaxLi>
		Describe the differences between the three stages of non-REM sleep
	</OpenstaxLi>
	<OpenstaxLi>
		Understand the role that REM and non-REM sleep play in learning and memory
	</OpenstaxLi>
</OpenstaxUl>
<OpenstaxParagraph>
	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. While awake, our brain wave activity is dominated by <OpenstaxTerm>beta waves</OpenstaxTerm>. As compared to the brain wave patterns while asleep, beta waves have the highest frequency (13–30 Hz) and lowest amplitude, and they tend to show more variability. As we begin to fall asleep, our brain wave activity changes. These changes can be visualized using an EEG and are distinguished from one another by both the frequency and amplitude of the brain wave. The frequency of a brain wave is how many brain waves occur in a second, and frequency is measured in Hertz (Hz). Amplitude is the height of the brain wave (<a href="#Figure_04_03_SleepCycle">Figure 4.7</a>). Sleep can be divided into two different general phases: REM sleep and non-REM (NREM) sleep. <OpenstaxTerm>Rapid eye movement (REM)</OpenstaxTerm> 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, <OpenstaxTerm>non-REM (NREM)</OpenstaxTerm> sleep 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, typically followed by REM sleep. In this section, we will discuss each of these stages of sleep and their associated patterns of brain wave activity. 
</OpenstaxParagraph>
<OpenstaxFigure id="Figure_04_03_SleepCycle" src="https://openstax.org/apps/archive/20240226.174525/resources/54c23b520871d442d2aec34fa6550e639c3d3bec" 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 REM. The wave amplitude is highest in late stage 2, and in the middle of stage 3 until REM. The wavelength is longer from late stage 2 through stage 3." mediaType="image/jpg" width="731" height="421" />
<OpenstaxFigureText width="731">
	<strong>Figure 4.7</strong> Brainwave activity changes dramatically across the different stages of sleep. (credit "sleeping": modification of work by Ryan Vaarsi)
</OpenstaxFigureText>

4.3 Stages of Sleep

1 Introduction to Psychology

1.1 What Is Psychology?

1.1.1 Why Study Psychology?

1.2 History of Psychology

1.2.1 Wundt and Structuralism

1.2.2 Functionalism

1.2.3 Freud and Psychoanalytic Theory

1.2.4 Wertheimer, Koffka, Köhler, and Gestalt Psychology

1.2.5 Pavlov, Watson, Skinner, and Behaviorism

1.2.6 Maslow, Rogers, and Humanism

1.2.7 The Cognitive Revolution

1.2.8 Multicultural And Cross-Cultural Psychology

1.2.9 Women in Psychology

1.3 Contemporary Psychology

1.3.1 Biopsychology and Evolutionary Psychology

1.3.2 Sensation and Perception

1.3.3 Cognitive Psychology

1.3.4 Developmental Psychology

1.3.5 Personality Psychology

1.3.6 Social Psychology

1.3.7 Industrial-Organizational Psychology

1.3.8 Health Psychology

1.3.9 Sport and Exercise Psychology

1.3.10 Clinical Psychology

1.3.11 Forensic Psychology

1.4 Careers in Psychology

1.4.1 Other Careers in Academic Settings

1.4.2 Career Options Outside of Academic Settings

2 Psychological Research

2.1 Why Is Research Important?

2.1.1 Use of Research Information

2.1.2 NOTABLE RESEARCHERS

2.1.3 The Process of Scientific Research

2.2 Approaches to Research

2.2.1 Clinical or Case Studies

2.2.2 Naturalistic Observation

2.2.3 Surveys

2.2.4 Archival Research

2.2.5 Longitudinal and Cross-Sectional Research

2.3 Analyzing Findings

2.3.1 Correlational Research

2.3.2 Causality: Conducting Experiments and Using the Data

2.3.3 Reliability and Validity

2.4 Ethics

2.4.1 Research Involving Human Participants

2.4.2 Research Involving Animal Subjects

3 Biopsychology

3.1 Human Genetics

3.1.1 Genetic Variation

3.1.2 Gene-Environment Interactions

3.2 Cells of the Nervous System

3.2.1 Neuron Structure

3.2.2 Neuronal Communication

3.2.3 Neurotransmitters and Drugs

3.3 Parts of the Nervous System

3.3.1 Peripheral Nervous System

3.4 The Brain and Spinal Cord

3.4.1 The Spinal Cord

3.4.2 The Two Hemispheres

3.4.3 Forebrain Structures

3.4.4 Midbrain and Hindbrain Structures

3.4.5 Brain Imaging

3.5 The Endocrine System

3.5.1 Major Glands

4 States of Consciousness

4.1 What Is Consciousness?

4.1.1 Biological Rhythms

4.1.2 Problems With Circadian Rhythms

4.2 Sleep and Why We Sleep

4.2.1 What is Sleep?

4.2.2 Why Do We Sleep?

4.3.1 NREM Stages of Sleep

4.3.2 REM Sleep

4.4 Sleep Problems and Disorders

4.4.1 Insomnia

4.4.2 Parasomnias

4.4.3 Sleep Apnea

4.4.4 Narcolepsy

4.5 Substance Use and Abuse

4.5.1 Substance Use Disorders

4.5.2 Drug Categories

4.6 Other States of Consciousness

4.6.1 Hypnosis

4.6.2 Meditation

5 Sensation and Perception

5.1 Sensation versus Perception

5.1.1 Sensation

5.1.2 Perception

5.2 Waves and Wavelengths

5.2.1 Amplitude and Wavelength

5.2.2 Light Waves

5.2.3 Sound Waves

5.3 Vision

5.3.1 Anatomy of the Visual System

5.3.2 Color and Depth Perception

5.4 Hearing

5.4.1 Anatomy of the Auditory System

5.4.2 Pitch Perception

5.4.3 Sound Localization