Chapter summary imageWhat causes us to sleep, dream, or even become hypnotized?

HOW DO DIFFERENT LEVELS OF CONSCIOUSNESS FUNCTION?

  • During minimal consciousness, we only dimly perceive the environment and might respond to a stimulus without full awareness of it (for example, during sleep).
  • During full consciousness, we are aware of our environment and of our own thoughts and mental state.
  • Self-consciousness is the highest level of consciousness; it enables us to reflect on our own identity.

HOW DOES CONSCIOUSNESS CHANGE WHILE WE SLEEP AND DREAM, AND WHY?

  • The body’s circadian rhythm controls sleep patterns.
  • The sleep cycle consists of several stages. Stage one is a very short period characterized by slow breathing and irregular brainwaves, stage two is a brief period characterized by bursts of brain activity, and stages three and four are longer periods of deep sleep.
  • After we complete stage four sleep, we cycle back through stages three and two sleep and enter REM sleep, in which heart rate and breathing increase and brainwaves become fast and irregular.
  • This cycle occurs every 90 minutes throughout the night. Stages three and four sleep periods decrease in length and eventually disappear, while REM sleep periods lengthen over the course of the night.

HOW CAN HYPNOSIS AND MEDITATION ALTER CONSCIOUSNESS?

  • Hypnosis is an altered state of consciousness achieved through social interaction. It may cause dissociation, a split in consciousness that allows some simultaneous thoughts and behaviours to occur separately from others.
  • Meditation is a process by which people can achieve a state of deep mental calm through concentration or mindfulness.

HOW DO PSYCHOACTIVE SUBSTANCES ALTER OUR CONCIOUSNESS?

  • Drugs that alter our consciousness are called psychoactive substances.
  • Psychoactive drugs include stimulants (caffeine, nicotine, cocaine), depressants (alcohol, marijuana), opiates (morphine, heroin), and hallucinogens (LSD, marijuana).
  • All psychoactive substances affect our consciousness by either increasing or decreasing neural activity.
  • Antagonists, such as alcohol, reduce neural activity while agonists, such as cocaine, increase neural activity.
  • Drugs activate the wanting system in our brain and can lead to physical and psychological dependence.
  • Withdrawal symptoms occur after we develop a tolerance for a drug, and these are signs that physical drug dependence (addiction) has occurred.
  • Psychological dependence is a major cause for relapse because recovering drug users continue to crave the effects of the drug.
  • Drugs differ in their addictive potential. The quicker the drug’s effects are felt, the shorter the effects last, the more intense the effects are, and severe withdrawal symptoms make a drug highly addictive.