Sleep as a Psychological Construct

Consciousness and Altered States

• Consciousness: Our awareness of our own existence, sensations, thoughts, and environment. It exists on a continuum.
• Normal Waking Consciousness: The state of clear, organized alertness.
• Altered State of Consciousness (ASC): Any state different from normal waking consciousness in terms of awareness, thoughts, feelings, and behaviors.
  • ASC can be naturally occurring (e.g., sleep, daydreaming) or induced (e.g., hypnosis, meditation, drugs).
• Sleep: A naturally occurring altered state of consciousness characterized by reduced awareness, control, and responsiveness to external stimuli.

KEY TAKEAWAY: Sleep is a naturally occurring altered state of consciousness, distinct from normal waking consciousness.

Sleep as a Psychological Construct

• Psychological Construct: A concept used to describe psychological phenomena that cannot be directly observed or measured, but is understood to exist.
  • Examples: Intelligence, memory, consciousness, and sleep.
• Characteristics of Sleep:
  • Reduced ability to control behaviour.
  • Reduction in control over thoughts.
  • Less accurate understanding of time passage.
  • Perceptual and cognitive distortions.

VCAA FOCUS: Understanding the characteristics of sleep is important for exam questions relating to altered states of consciousness.

Stages of Sleep: REM and NREM

Sleep is broadly categorized into two main types:

• Rapid Eye Movement (REM) Sleep:
  • Characterized by rapid eye movements, high brain activity (similar to wakefulness), and muscle paralysis.
  • Associated with dreaming.
  • Makes up approximately 20-25% of a typical sleep episode.
• Non-Rapid Eye Movement (NREM) Sleep:
  • Characterized by a lack of rapid eye movements and generally lower brain activity.
  • Subdivided into three stages (formerly four).
  • Makes up approximately 75-80% of a typical sleep episode.

NREM Sleep Stages

Note: NREM stage 4 has been merged into NREM stage 3.

Sleep Cycle

• Sleep Episode: The total duration of time spent asleep.
• Sleep Cycle: A recurring pattern of NREM and REM sleep stages that repeats approximately every 90 minutes during a sleep episode.
• A typical sleep cycle progresses from NREM 1 to NREM 2 to NREM 3, then back to NREM 2, followed by REM sleep.
• The proportion of time spent in each stage changes throughout the night; NREM 3 is more prominent in the early cycles, while REM sleep becomes longer in later cycles.
• Hypnogram: A sleep graph that visually represents the stages of sleep throughout a sleep episode.

EXAM TIP: Be able to describe the characteristics of each sleep stage and how they change throughout a typical sleep cycle.

Measuring Physiological Responses During Sleep

To objectively study sleep, researchers use various physiological measures:

• Electroencephalography (EEG):
  • Detects and records electrical activity in the brain using electrodes placed on the scalp.
  • Used to identify different stages of sleep based on brain wave patterns (alpha, beta, theta, delta).
  • Beta waves = awake and alert.
  • Alpha waves = awake and relaxed.
  • Theta waves = light sleep.
  • Delta waves = deep sleep.
• Electromyography (EMG):
  • Detects and records electrical activity in muscles.
  • Used to measure muscle tone and identify muscle paralysis during REM sleep.
• Electro-oculography (EOG):
  • Detects and records eye movements using electrodes placed near the eyes.
  • Used to identify rapid eye movements during REM sleep.
• Sleep Diaries:
  • Self-reported records of an individual’s sleep patterns, including bedtime, wake-up time, sleep duration, and subjective sleep quality.
  • Can provide valuable information about sleep habits and potential sleep problems.
• Video Monitoring:
  • Records physical behaviors during sleep, such as tossing and turning, sleepwalking, and sleep talking.
  • Can help identify sleep disorders and unusual sleep behaviors.

Summary Table: Physiological Measures of Sleep

STUDY HINT: Create flashcards for each physiological measure, including what it detects and how it’s used in sleep research.

REMEMBER: EEG, EMG, and EOG provide objective physiological data, while sleep diaries provide subjective self-reported data.