Consciousness and Sleep-Wake States

Consciousness

  • Consciousness: Awareness of the world and one's existence within it.

States of Consciousness

  • Accepted States:
    • Alertness
    • Sleep
    • Dreaming
    • Altered States (hypnosis, meditation, drug-induced states, sickness, dementia, delirium, coma)

Alertness

  • Definition: Awake and able to think; perceive, process, assess, and verbalize information.
  • Physiological Arousal: Increased heart rate, breathing rate, blood pressure.
  • Cortisol Levels: Tend to be higher.
  • EEG Waves: Indicate a brain in the wakened state.
  • Neurological Circuits:
    • Prefrontal Cortex: Maintains alertness.
    • Reticular Formation (Reticular Activation System): Located in the brainstem; communicates with the prefrontal cortex to keep the cortex awake and alert.
  • Brain Injury: Disruption of these circuits can result in coma.

Sleep

  • Importance: Crucial for cognitive performance; long-term sleep deprivation linked to diminished cognitive performance and chronic diseases (diabetes, obesity).

Stages of Sleep

  • Studied via EEG (electroencephalography): Records an average of electrical patterns in the brain.
  • EEG Patterns:
    • Beta waves
    • Alpha waves
    • Theta waves
    • Delta waves
    • REM

Brainwave Activity

  • Beta Waves:
    • High frequency.
    • Occur when alert or attending to a mental task.
    • Neurons are randomly firing.
  • Alpha Waves:
    • Slower than beta waves.
    • Occur when awake but relaxing with eyes closed.
    • More synchronized than beta waves.
  • Stage 1 (NREM 1):
    • Theta Waves: Irregular waveforms with slower frequencies and higher voltages.
  • Stage 2 (NREM 2):
    • Theta waves.
    • Sleep Spindles: Bursts of high-frequency waves.
    • K Complexes: Singular high-amplitude waves.
  • Stage 3 (NREM 3) / Slow Wave Sleep (SWS):
    • Delta Waves: Slow frequency, high voltage sleep waves.
    • Difficult to rouse someone.
    • Associated with cognitive recovery, memory consolidation, and increased growth hormone release.
  • Non-Rapid Eye Movement (NREM) Sleep: Collective name for stages 1-3.
  • Rapid Eye Movement (REM) Sleep:
    • Arousal levels reach wakefulness, but muscles are paralyzed.
    • Also called paradoxical sleep (heart rate, breathing, EEG mimic wakefulness).
    • Dreaming is most likely to occur.
    • Associated with memory consolidation:
      • Procedural memory consolidation.
      • SWS with declarative memory consolidation.

Sleep Cycles

  • Definition: A single complete progression through the sleep stages.
  • Changes During the Night:
    • Early in the night: SWS predominates.
    • Later in the night: REM sleep predominates.
  • Changes Over Lifespan:
    • Length of sleep cycle increases from approximately 50 minutes in children to 90 minutes in adults.
    • Children spend more time in SWS than adults.
  • Disruption of Sleep Cycles: Can cause health problems; disruption of SWS and REM can result in diminished memory.
  • Sleep Deprivation: Diminished cognitive performance, negative effects on mood, problem-solving, and motor skills.

Sleep and Circadian Rhythms

  • Regulation: Daily cycle of waking and sleeping regulated by internally generated circadian rhythms.
  • Circadian Rhythm: Approximates a 24-hour cycle; affected by external cues (e.g., light).
  • Biochemical Signals:
    • Melatonin: Serotonin-derived hormone from the pineal gland; increased by decreased light.
    • Cortisol: Steroid hormone from the adrenal cortex; levels increase in the early morning due to the release of corticotropin-releasing factor (CRF) from the hypothalamus. CRF causes the release of adrenocorticotropic hormone (ACTH) from the anterior pituitary, which stimulates cortisol release; contributes to wakefulness.

Dreaming

  • Historical Perspectives: Ancient Egyptians (messages from the supernatural world), Greeks (messages from the gods).
  • REM Sleep: Most dreaming occurs during REM (75% of dreaming).
    • REM dreams are longer and more vivid than NREM dreams.

Theories of Dreaming:

  • Activation Synthesis Theory: Dreams are caused by widespread random activation of neural circuitry. The cortex tries to stitch unrelated information together.
  • Problem-Solving Dream Theory: Dreams are a way to solve problems; untethered by the rules of the real world.
  • Cognitive Process Dream Theory: Dreams are merely the sleeping counterpart of the stream of consciousness.
  • Neurocognitive Models: Seek to unify biological and psychological perspectives on dreaming by correlating the subjective cognitive experience of dreaming with measurable physiological changes.

Sleep-Wake Disorders

  • Dyssomnias: Disorders that make it difficult to fall asleep, stay asleep, or avoid sleep.
    • Insomnia: Difficulty falling asleep or staying asleep; related to anxiety, depression, medication, or disruption of sleep cycles and circadian rhythm.
    • Narcolepsy: Lack of voluntary control over the onset of sleep.
      • Symptoms: Cataplexy, sleep paralysis, hypnogogic and hypnopompic hallucinations.
    • Sleep Apnea: Inability to breathe during sleep; obstructive (physical blockage) or central (brain fails to send signals to the diaphragm).
  • Parasomnias: Abnormal movements or behaviors during sleep.
    • Night Terrors: Intense anxiety during slow-wave sleep (SWS); common in children; difficult to wake the child and usually no memory of the dream.
    • Sleepwalking (Somnambulism): Usually occurs during SWS; may perform complex activities; no recollection of the event.

Sleep Deprivation:

  • Results in irritability, mood disturbances, decreased performance, and slowed reaction time.
  • Extreme deprivation can cause psychosis.
  • REM Rebound: Earlier onset and greater duration of REM sleep after sleep deprivation.

Hypnosis

  • Definition: A state in which a person appears to be in control of his or her normal functions but is in a highly suggestible state.
  • Hypnotic Induction: The hypnotist seeks to relax the subject and increase the subject's level of concentration.
  • Applications: Pain control, psychological therapy, memory enhancement, weight loss, and smoking cessation.
  • Requires a willing personality and lack of skepticism.

Meditation

  • Definition: Quieting of the mind whether spiritual or religious or relaxed to stress reduction.
  • Used for counseling and psychotherapy to produce relaxation and relief from anxiety.
  • Physiological Changes: Decreased heart rate and blood pressure.
  • EEG: Resembles stage one sleep with theta and slow alpha waves.