Theories of Dreaming

• The main topics are sleep, dreaming, and circadian rhythms

The Physiological and Behavioral Correlation of Sleep

• 1930s: Major changes in human EEG, or Electroencephalogram, during a night's sleep were first observed.
• 1953: Aserinsky and Kleitman discovered rapid eye movements (REM) occur under closed eyelids of sleeping subjects during low-voltage, fast EEG activity.
• 1962: Berger and Oswald found a loss of electromyographic activity in the neck muscles during the same sleep periods.

Standard Psychophysiological Measures of Sleep

• Electroencephalogram (EEG) measures electrical energy of the brain, recorded via scalp electrodes
• Electrooculogram (EGO) measures eye movement.
• Electromyogram (EMG) measures electrical activity of muscles.

Awake vs REM vs NREM

• Awake EEG: brain activity
• REM EEG; brain activity
• NREM EEG: brain avtivity
• Awake EMG: muscle activity
• REM EMG: muscle activity
• NREM EMG: muscle activity
• Awake EOG: eye movement
• REM EOG: eye movement
• NREM EO: eye movement

The 5 Stages of Sleep

• EEG of a subject during sleep is divided into stages 1, 2, 3, and 4.
• As a subject’s eyes shut to prepare to sleep, alpha waves (8 to 12 Hz) punctuate the low amplitude, high-frequency EEG of active wakefulness.
• Stage 1 sleep: low amplitude, high-frequency signal similar to active wakefulness, but slower.
• Stage 1 is considered the transition between wakefulness and sleep, characterized by theta waves.
• As the subject continues to sleep, EEG waves progressively increase in amplitude and slow in frequency across stages 2, 3, and 4.
• Stage 2 sleep is punctuated by K complexes (single large negative wave followed by a single large positive wave) and sleep spindles (1-2 second waxing and waning bursts of 12 to 14 Hz waves).
• During Stage 2, body temperature decreases and the heart begins to slow down; stage lasts about 20 minutes.
• Stage 3 sleep is defined by occasional presence of delta waves, the largest, slowest EEG waves, with a frequency of 1-2 Hz
• Stage 3 is transition between light and very deep sleep when deep, slow brain waves (delta waves) begin to appear.
• Stage 4 sleep: also known as delta sleep because of the predominance of delta waves, lasts around 30 minutes.
• Stage 5 or REM (rapid eye movement) sleep is characterized by rapid eye movements, loss of core muscle tone, and emergent stage 1.
• Physiological correlates of Stage 5 include increased cerebral activity (oxygen consumption, blood flow, and neural firing in many structures) nearing waking levels along with increased autonomic nervous system activity (blood pressure, pulse, and respiration).
• During Stage 5, there is Occasional twitching of extremity muscles and some degree of penile and clitoral erection.
• High correlation exists between REM sleep and dream recall, which allows to test common beliefs about dreaming
• REM sleep related beliefs that have been subjected to empirical tests are; external stimuli can become incorporated into dreams, dreams last only an instant, some people never dream, penile erections are commonly assumed to be indicative of dreams of sexual content, and finally, sleep talking or sleep walking occurs during sleep
• Emergent sleep 1, also called paradoxical sleep, has EEG and automatic activities similar to wakefulness.
• After the first sleep cycle (Stage 1 to REM Stage), the rest of the night is spent alternating back and forth through the stages.
• Sleep cycles are about 90 minutes long, therefore people typically go through 4 or 5 cycles a night.

Interpretation of Dreams

• Sigmund Freud believed dreams are triggered by unacceptable repressed wishes, referring to them as the "royal road to the unconscious".
• Activation-synthesis theory developed by J. Allan Hobson and Robert McCarley suggests the physiological processes of the brain cause dreams.
• Circuits in the brain stem activate during REM, then limbic system areas involved in emotions, sensations, and memories (amygdala and hippocampus) become active.
• Cerebral cortex synthesizes signals and tries to interpret them
• The brain synthesizes and interprets internal activity and attempts to create meaning from these signals, resulting in dreaming.
• Although activation-synthesis model relies on physiological processes, it doesn't imply that dreams are meaningless
• According to Hobson, dreaming may be our most creative conscious state allowing cognitive elements to produce novel information.
• Lucid dreams refer to dreams in which the dreamer is aware that he or she is dreaming which allows them to influence the course of the dreams.

Why Do We Sleep?

• Recuperation Theory believes being awake disrupts the body's homeostasis, thus sleep is needed to restore it.
• Circadian Theory argues sleep evolved to keep animals inactive when they don't need to engage in survival activities.

Circadian Sleep Cycles

• Circadian rhythm refers to the diurnal (daily) cycles of body functions;
• An example of circadian rhythm is the sleep-wake cycle.
• Zeitgebers, or time givers, are environmental cues (e.g., the light-dark daily cycle) that can control the timing of circadian rhythms.
• Two disruptions of circadian rhythmicity:
  • Jet lag: occurs when zeitgebers are accelerated during eastern flights (phase advances) or decelerated during western flights (phase delays).
  • Shift work: workers must adjust their natural sleep-wake cycles when zeitgebers do not change.

Effects of Sleep Deprivation

• According to the Recuperation Theory, long wakefulness periods will produce physiologcial and behavioral disturbances that will worsen as sleep deprivation continues,
• After deprivation, much missed sleep will be regained.
• According to Circadian Theory, there should be no debilitating effects of sleep deprivation other than an increased tendency to fall asleep, this will be greatest during phases when subjects normally sleep
• There will be little or no compensation for the lost sleep once the period of deprivation has ended.
• The Suprachiasmatic Nucleus (SCN) in the hypothalamus serves as the circadian rhythm control center for sleep and body temperature.
• Light influence on the suprachiasmatic nuclei and the output rhythms.

Biochemistry of the Circadian Rhythm

• SCN regulates waking and sleeping by controlling activity levels in other brain areas, including the pineal gland which releases melatonin hormone.
• Melatonin secretion starts to increase 2 or 3 hours before bed time, which feeding back to reset clock through the SCN's receptors.

Drugs That Affect Sleep

• Hypnotic drugs increase drowsiness, decrease time it takes to fall asleep, reduce awakenings and increases total sleep time,
• Benzodiazepines (e.g., Valium and Librium) are examples of hypnotic drugs from the class of anxiolytic drugs.
• Antihypnotic drugs, sleep-reducing drugs, can include stimulants (e.g., cocaine, amphetamine, caffeine) and tricyclic antidepressants.
• Antihypnotic drugs often suppress REM sleep, are often addictive and have side effects.

Sleep Disorders

• Many sleep disorders fall into dyssomnia and parasomnia, which are the two major categories.
• Dyssomnia is characterized by disturbances in the amount, quality and timing of sleep (e.g., insomnia, hypersomnia, narcolepsy).
• Parasomnia is characterized by unnatural and abnormal behaviors, emotions and perception which occur during sleep (e.g. somnambulism, nightmares, sleep terrors).
• Insomnia is difficulty initiating and maintaining sleep.
• Hypersomnolence is excessive sleepiness and inability to feel refreshment from sleep.
• Narcolepsy characterized by repeated, brief and irresistible daytime sleep attacks.
• Sleep apnea is sleep is repeatedly disturbed via momentary interruptions in breathing.
• Restless legs syndrome involves tension or uneasiness in the legs that keeps a person from falling asleep.
• Sleep state misperception is a condition wherein people mistakenly perceive their sleep as wakefulness.
• Somnambulism is sleep walking.
• REM behavior disorder causes violent and vigorous body movements during REM sleep.
• Night terrors – experiences of intense anxiety from which a person awakens screaming in terror.
• Periodic limb movement disorder is characterized by repeated involuntary movement of the legs and arms especially when starting to fall asleep.
• Bruxism is characterized by teeth-grinding during sleep.
• Sexomnia is a condition in which a person will engage in sexual acts while still asleep and will not remember it afterward.

Explore the theories behind dreaming, including paradoxical sleep, Freud's trigger hypothesis, and the activation-synthesis theory. Understand how the brain attempts to create meaning during REM sleep and the involvement of the limbic system. Differentiate Freud's theory from the activation-synthesis theory.