Overview
This lecture explains the stages of sleep, differentiates between REM and non-REM (NREM) sleep, describes brain wave activity in each stage, and discusses the role of sleep in learning, memory, and dreaming.
Sleep Stages Overview
- Sleep consists of several stages with distinct patterns of brain wave activity.
- Awake brain waves are beta waves: high frequency, low amplitude, and variable.
- Sleep is divided into REM (rapid eye movement) and non-REM (NREM) stages.
NREM Sleep Stages
- NREM sleep has three stages, each with specific characteristics and brain waves.
- Stage 1 NREM is a transitional phase with alpha and then theta waves, reduced breathing, heart rate, muscle tension, and temperature.
- Stage 1 sleep is light and easy to wake from.
- Stage 2 NREM is marked by theta waves, sleep spindles (short bursts linked to learning/memory), and K-complexes (high amplitude responses to stimuli).
- Stage 3 NREM is deep, slow-wave sleep with delta waves (low frequency, high amplitude); difficult to awaken from and critical for feeling refreshed.
REM Sleep
- REM sleep shows brain activity similar to wakefulness and is when most dreaming occurs.
- REM sleep involves paralysis of voluntary muscles except those for circulation and breathing.
- REM is called paradoxical sleep due to active brain and inactive muscles.
- REM sleep is important for learning, memory, emotional processing, and is homeostatically regulated (REM rebound after deprivation).
Sleep Cycle Patterns
- Typical sleep cycles progress through NREM stages and REM, repeating about every 90 minutes.
- Deep sleep (stage 3) is more common in the first half of the night.
Dreaming and Theories
- Freud believed dreams reveal unconscious desires (manifest vs latent content).
- Jung proposed dreams connect to universal archetypes in the collective unconscious.
- Cartwright found dreams often reflect personal daily concerns, supported by research.
- Hobson’s activation-synthesis theory suggests dreams result from the brain synthesizing random neural activity during REM.
- Lucid dreams occur when a person is aware they are dreaming and can control the dream.
Key Terms & Definitions
- REM Sleep — Rapid eye movement sleep with vivid dreams and muscle paralysis.
- NREM Sleep — Non-rapid eye movement sleep, includes stages 1–3.
- Sleep Spindle — Brief burst of higher frequency brain wave during stage 2, linked to learning/memory.
- K-complex — High amplitude brain wave in stage 2, responding to external stimuli.
- Delta Wave — Low frequency, high amplitude brain wave in deep sleep (stage 3).
- REM Rebound — Increased REM sleep following deprivation.
- Manifest Content — Actual storyline/content of a dream.
- Latent Content — Hidden psychological meaning of a dream.
- Collective Unconscious — Jung’s term for shared universal information reflected in dreams.
- Activation-Synthesis Theory — View that dreams result from the brain interpreting neural activity during REM.
- Lucid Dream — Dream in which the dreamer is aware and may control the dream.
Action Items / Next Steps
- Watch the recommended video about sleep stages (link provided in lecture).
- Review key terms and their definitions for understanding and exam preparation.