Compare states of consciousness and explain sleep and dreaming, including how they are measured.

What this dot point is asking

The TASC psychobiological module pairs the functioning brain with consciousness. Consciousness is our awareness of internal and external events, and it varies continuously, so this dot point asks you to describe those variations and the methods used to study them.

States of consciousness

Normal waking consciousness (NWC) is the state of clear awareness of yourself and your environment when awake and alert, with controlled, selective attention and an accurate sense of time. An altered state of consciousness (ASC) is any state that differs noticeably from NWC, such as sleep, daydreaming, hypnosis, meditation, or states induced by alcohol or other drugs. ASCs typically involve changes in attention, perception, time orientation, emotional awareness and self-control.

Measuring consciousness

Because consciousness is private, psychologists use both objective physiological tools and subjective self-report.

• EEG (electroencephalograph): records the brain's electrical activity as brain waves. Beta waves (high frequency, low amplitude) mark alert wakefulness; alpha waves mark relaxed wakefulness; theta and delta waves (low frequency, high amplitude) appear in sleep.
• EOG (electro-oculograph): records eye movements, used to detect the darting eyes of REM sleep.
• EMG (electromyograph): records muscle tension, which falls sharply during REM sleep.
• Subjective measures include sleep diaries and self-reports, which add detail but can be unreliable.

The stages of sleep

Sleep cycles through non-REM (NREM) and REM stages roughly every 90 minutes. NREM has stages of progressively deeper sleep, with slow delta waves dominating the deepest stage and the body repairing tissue. REM (rapid eye movement) sleep shows fast, awake-like brain waves, darting eyes, near-total muscle paralysis (atonia), and is when most vivid dreaming occurs. Across a night, NREM dominates early and REM periods lengthen toward morning.

Circadian and ultradian rhythms

A circadian rhythm is a biological cycle of about 24 hours, the most important being the sleep-wake cycle, regulated by the suprachiasmatic nucleus in the hypothalamus and by melatonin from the pineal gland in response to light. An ultradian rhythm is a cycle shorter than 24 hours, such as the 90-minute sleep cycle. Disruption of circadian rhythm, as in jet lag or shift work, causes fatigue and poor concentration until the body clock realigns.

Sleep deprivation

Going without sufficient sleep produces a sleep debt. Effects include impaired concentration, slowed reaction time, irritability, poorer memory consolidation and, with severe deprivation, microsleeps and even hallucinations. Partial sleep deprivation (too little sleep) is more common than total deprivation, and its cognitive and emotional effects accumulate over successive nights.

Theories of dreaming

• Psychodynamic (Freud): dreams express unconscious wishes, with manifest content (the storyline) disguising latent content (the hidden meaning). This is rich but hard to test.
• Activation-synthesis (Hobson and McCarley): dreams are the cortex's attempt to make sense of random neural activity generated during REM sleep, so the story is constructed after the fact.
• Consolidation and information-processing views: dreaming helps the brain process and store the day's memories, linking REM sleep to learning.

Putting it together

Frame consciousness as a continuum from full alertness to deep sleep, and use the EEG, EOG and EMG to justify how each state is identified. Describe the NREM and REM cycle, link the sleep-wake cycle to circadian rhythm, and outline sleep-deprivation effects. For dreaming, contrast at least two theories. Naming the measurement tools and the dream theories is what lifts an answer from description to the analysis TASC rewards.