Sleep and Dreaming

Sleep Stages — Structured Notes

Overview

• A full sleep cycle lasts 90–110 minutes.

• EEG (electroencephalograph) measures brain waves across stages.

• Two major categories:

  • NREM (non-REM) — Stages 1–4

  • REM — Dream-heavy, paradoxical sleep

Brain Waves

• Awake but relaxed: Alpha waves

  • Smooth, slow rhythm patterns

NREM Sleep Stages

Stage 1 (NREM-1)

• Lightest sleep

• Heart rate slows

• Hypnic jerks may occur

• Brief visual hallucinations (like flashes or shapes)

• Transitional stage

Stage 2 (NREM-2)

• Deeper than Stage 1

• EEG shows sleep spindles (sudden bursts of rapid waves)

• Heart rate slows more

• Body temperature drops

Stage 3 & Stage 4 (NREM-3/4) — Deep Sleep / Slow-Wave Sleep

• Delta waves dominate (large, slow waves)

• Most restorative stage

• Very hard to wake someone

• If woken: grogginess and disorientation

• Breathing is slow and steady

Important: Parasomnias occur here

✔ Sleepwalking
✔ Sleeptalking
✔ Bedwetting (nocturnal enuresis)
✔ Night terrors

These occur because the body is NOT paralyzed during NREM sleep.

REM Sleep

• Rapid Eye Movement

• Occurs after cycling back through NREM (1 → 2 → 3 → 4 → 3 → 2 → 1 → REM)

• First REM lasts ~10 minutes; later cycles can last up to an hour

• Dreams occur mostly here

• Brain is highly active

Key characteristics:

• Motor output inhibited (paralysis) to prevent acting out dreams

• Genital arousal in both sexes regardless of dream theme

• Heart rate and breathing become irregular

• Memory consolidation may occur

Sleep Disorders Mentioned

Insomnia

• Difficulty falling or staying asleep

• Affects 10–15% of people

Sleep Apnea

• Person stops breathing repeatedly during sleep

• Often snores loudly or gasps

• Prevents deep sleep, causes daytime fatigue

Narcolepsy

• Sudden attacks of overwhelming sleepiness

• Can include REM sleep attacks with paralysis

• Often triggered by strong emotion

Dreaming Theories

Freud’s Theory

• Dreams have:

  • Manifest content (literal storyline)

  • Latent content (hidden meaning, often unconscious desires)

• No scientific evidence supports this model

Activation–Synthesis Theory

• Dreams = brain’s attempt to make sense of random neural firing in the pons during REM

Information-Processing Theory

• Dreaming helps sort and consolidate daily information

• Brain discards unnecessary data (reverse learning)

Circadian Rhythms

• 24-hour biological cycles controlling:

  • Hormones

  • Body temperature

  • Energy levels

• Continue even without light cues

Circadian Disruptions

Jet Lag

• Traveling across time zones disrupts rhythms

• Causes fatigue and confusion

Shift Work

• Night shifts disrupt rhythms

• Rotating shifts = worst adjustment

REM Rebound

• When deprived of REM sleep, the body compensates by entering REM more quickly and more intensely during the next sleep period

• Indicates REM is biologically important

NOTES: Circadian Rhythms, Sleep Stages, Disorders, and Theories

Circadian Rhythms

• Internal biological clock regulating sleep–wake cycles.

• Influences:

  • Hormone release (melatonin levels rise at night)

  • Body temperature

  • Energy levels

• Typically follows a 24-hour cycle but varies by person.

  • “Morning people” peak early.

  • “Night owls” peak later.

• Disruptions occur with:

  • Night shifts

  • Jet lag (travel across time zones)

• Effects of disruption:

  • Low energy

  • Poor coordination

  • Irregular sleep patterns

  • Feeling mentally “out of sync”

Night Terrors and Sleepwalking

• Occur during deep sleep (NREM Stage 3 and Stage 4).

• EEG shows delta waves during these stages.

• Night terrors:

  • Person may scream or appear terrified.

  • Not tied to dreams.

  • When awakened, person is confused and does not remember the incident.

• Sleepwalking:

  • Also occurs in deep sleep (stage 4).

  • Person walks or performs actions while asleep.

  • If awakened, person is confused and does not recall walking.

Seasonal Affective Disorder (SAD)

• Depression occurring mainly in autumn and winter.

• Caused by reduced sunlight exposure.

• More common in northern latitudes.

• Symptoms improve with light therapy.

• Affects mood, motivation, and daily functioning.

How Much Sleep Do You Need?

• Adults: ~8 hours 15 minutes per night.

• Teens: 8–9 hours per night to function optimally.

• Research findings:

  • Students with more sleep perform better academically.

  • Later school start times lead to:

    • Higher grades

    • Better behavior

    • Lower dropout rates

• Lack of sleep contributes to driving accidents at rates similar to alcohol impairment.

Why Do We Sleep?

Restorative Theory

• Sleep restores the body and mind.

• Replenishes energy and mental processes used during the day.

• Helps repair tissues and consolidate memory.