Consciousness, Sleep, and Drugs
Analyze states of consciousness, sleep stages, dreams, psychoactive drugs, tolerance, dependence, and altered states.
A lesson of AP Psychology, in Biological Bases of Behavior, about 10 minutes.
Consciousness, Sleep, and Psychoactive Drugs
By the end of this lesson, you will be able to describe states of consciousness, explain sleep stages and their functions, and classify psychoactive drugs by their effects.
Consciousness
Consciousness: our awareness of ourselves and our environment at any given moment.
Levels of consciousness:
- Conscious: currently aware; the spotlight of attention
- Preconscious: accessible but not currently in focus (your name, what you had for breakfast)
- Unconscious (Freudian): repressed material not accessible to awareness
- Nonconscious: biological processes never available to awareness (regulating heartbeat)
Altered states of consciousness: hypnosis, meditation, sleep, and psychoactive drug effects all produce states that differ from normal waking consciousness.
Sleep: Stages and Function
Circadian rhythms: ~24-hour biological cycles governed by the suprachiasmatic nucleus (SCN) in the hypothalamus; aligned with light/dark by the pineal gland (releasing melatonin in darkness).
NREM (Non-REM) sleep:
- Stage 1: transitional; hypnagogic hallucinations; easy to wake
- Stage 2: bursts of rapid brain activity (sleep spindles); harder to wake; eye movement stops
- Stage 3: slow-wave (delta wave) sleep; deep, restorative; growth hormone released; hardest to wake
REM sleep (Rapid Eye Movement): vivid dreaming occurs; brain is very active; motor cortex sends signals, but spinal cord is paralyzed (REM atonia — prevents acting out dreams). Memory consolidation occurs here.
Sleep cycle: NREM stages (1→2→3→back up) + REM, repeated ~4-5 times per night. Each cycle ~90 minutes. Later cycles have more REM, less slow-wave sleep.
Dreams
Why do we dream?
- Activation-synthesis theory (Hobson): the dreaming brain tries to make sense of random neural firing
- Freudian theory: dreams express unconscious wishes in disguised form (manifest vs. latent content)
- Memory consolidation theory: dreams help consolidate and organize memories
- Threat simulation theory: dreams rehearse threatening scenarios as preparation
REM sleep deprivation causes increased REM on recovery nights ("REM rebound").