Overview
This lecture explains the stages of sleep, differentiates between REM and non-REM sleep, describes their physiological characteristics, and explores the role of sleep in learning, memory, and dreaming.
Sleep Stages: General Concepts
- Sleep consists of various stages, each defined by characteristic brain wave patterns.
- Brain activity during wakefulness is dominated by high-frequency, low-amplitude beta waves.
- Sleep is divided into REM sleep and non-REM (NREM) sleep.
- REM sleep is noted for rapid eye movements and brain activity similar to wakefulness.
- NREM sleep is subdivided into three stages with distinct brain wave changes.
NREM Sleep Stages
- Stage 1: Transition between wakefulness and sleep with alpha and theta waves, slow heart rate, and relaxed muscles.
- Alpha waves (early stage 1): Lower frequency, higher amplitude, synchronized patterns, resemble relaxed wakefulness.
- Theta waves (late stage 1): Even lower frequency and higher amplitude than alpha waves.
- Easy to awaken from stage 1; people often deny being asleep.
- Stage 2: Body enters deep relaxation, theta waves dominate with sleep spindles and K-complexes.
- Sleep spindles: Brief bursts of high-frequency activity, may aid learning and memory.
- K-complexes: High amplitude patterns, often in response to external stimuli, may protect sleep.
- Stage 3: Deep or slow-wave sleep, characterized by low-frequency, high-amplitude delta waves.
- Heart rate and respiration slow significantly, very difficult to awaken.
- Increased alpha wave activity during stage 3 may result in unrefreshing sleep.
REM Sleep
- REM sleep features rapid eye movement and brain waves resembling wakefulness.
- Dreaming occurs during REM sleep.
- Body experiences muscle paralysis except for vital functions.
- REM is called paradoxical sleep due to high brain activity and muscle atonia.
- REM sleep is important for learning, memory, and emotional regulation.
- REM rebound: More REM sleep after deprivation, suggesting homeostatic regulation.
- Hypnogram shows typical progression through all sleep stages during the night.
Dream Theories
- Freud viewed dreams as access to the unconscious, distinguishing manifest (actual) and latent (hidden) content.
- Jung believed dreams tap into the collective unconscious and universal archetypes.
- Cartwright argued dreams reflect significant life events; her view is supported by evidence.
- Hobson's activation-synthesis theory sees dreams as the brain synthesizing random neural activity; later updates suggest dreams help with virtual reality construction (protoconsciousness).
- Lucid dreams occur when a person is aware they are dreaming and can control dream content.
Key Terms & Definitions
- REM Sleep — Rapid Eye Movement sleep, involving quick eye movements, dreaming, and muscle paralysis.
- NREM Sleep — Non-Rapid Eye Movement sleep, consists of three stages with progressively deeper sleep.
- Alpha Waves — Brain waves present in relaxed wakefulness and early stage 1 sleep.
- Theta Waves — Lower frequency, higher amplitude brain waves prominent in stage 1 and 2 sleep.
- Delta Waves — Very low frequency, high amplitude waves found in deep sleep (stage 3).
- Sleep Spindle — Brief bursts of high-frequency activity in stage 2, linked to learning.
- K-Complex — High-amplitude brain wave in stage 2, potentially protective response to stimuli.
- REM Rebound — The tendency to spend more time in REM after deprivation.
- Manifest Content — The literal storyline of a dream.
- Latent Content — The hidden psychological meaning of a dream.
- Collective Unconscious — Jung's idea of shared universal symbols and archetypes.
- Lucid Dream — A dream during which the dreamer is aware they are dreaming.
Action Items / Next Steps
- Watch assigned video on sleep stages.
- Review key terms and study the hypnogram illustrating sleep cycles.
- Prepare for questions on distinguishing REM from NREM stages and their characteristics.