Chapter 8- Wakefulness and Sleep

Biological Psychology: Wakefulness and Sleep

Introduction

• Early Views:
  • Early psychologists thought wakefulness and sleep depended on external stimuli.
• Curt Richter (1922):
  • Proposed that the body generates its own cycles of activity and inactivity.

Endogenous Rhythms

• Endogenous Circannual Rhythms:
  • Internal mechanisms operating on a yearly cycle.
  • Examples: bird migration, food storage for winter.
• Endogenous Circadian Rhythms:
  • Internal mechanisms operating on a roughly 24-hour cycle.
  • Affect:
    • Sleep cycle
    • Eating and drinking frequency
    • Body temperature
    • Hormone secretion
    • DNA repair
    • Mood changes

Activity Record Example

• Flying Squirrel in Constant Darkness:
  • Waking period starts earlier each day.
  • Sleep period starts earlier each day.

Daily Pattern of Body Temperature

• Body Temperature:
  • Lowest: ~2 hours after sleep onset.
  • Peak: ~6 hours before sleep onset.

Reported Positive Mood Over Time

• Mood Fluctuation:
  • Mood varies throughout the day.
  • The data reflects mood relative to an average.

Setting and Resetting the Biological Clock

• Alignment:
  • Internal clock must align with the external world.
• Intrinsic Period:
  • The internal clock runs slightly longer than 24 hours without external cues.
• Resetting:
  • Needs periodic resetting (e.g., daylight saving time).
• Zeitgeber:
  • A stimulus that resets the rhythm ("time-giver").
  • Examples: sunlight, exercise, meals, temperature.
• Weak Zeitgebers:
  • Artificial light can cause mood and performance issues.
• Blind Individuals:
  • May face challenges in rhythm regulation.

Sun Time vs. Social Time

• Competing Influences:
  • Sun time and social time affect sleep patterns.

Jet Lag

• Definition:
  • Disruption of circadian rhythms due to crossing time zones.
• Cause:
  • Mismatch between internal clock and external time.
• Symptoms:
  • Daytime sleepiness, nighttime sleeplessness, impaired concentration.
• Direction of Travel:
  • Westward travel: "Phase-delays" circadian rhythms.
  • Eastward travel: "Phase-advances" circadian rhythms.

Night Work

• Sleep Duration:
  • Depends on when one sleeps.
• Circadian Rhythm Shift:
  • Night work doesn't reliably change it.
• Persistent Effects:
  • Groggy feeling, poor daytime sleep, body temperature peaks during sleep.
• Adjustment Strategies:
  • Dark room for daytime sleep, bright lights during night work.
• Light Wavelength:
  • Consideration of short- vs. long-wavelength light.

Age Differences in Circadian Rhythms

• Age-Related Changes:
  • Sleep patterns vary with age, especially during adolescence.

Mechanisms of the Biological Clock

• Key Components:
  • The suprachiasmatic nucleus (SCN)
  • Genes producing specific proteins
  • Melatonin levels

The Suprachiasmatic Nucleus (SCN)

• Control Center:
  • Main center for circadian rhythms of sleep and temperature.
• Location:
  • Above the optic chiasm, part of the hypothalamus.
• Damage Effects:
  • Inconsistent body rhythms, desynchronization from light/dark patterns.
• Automatic Rhythm Generation:
  • The SCN generates rhythms autonomously.
• Transplantation:
  • Transplanted SCN tissue maintains its rhythm.

SCN Location

• Anatomical Position:
  • Illustrations show SCN's location in rats and humans relative to other brain structures.

How Light Resets the SCN

• Retinohypothalamic Path:
  • Light resets SCN via this small optic nerve branch.
  • Direct path from retina to SCN.
• Melanopsin:
  • Special ganglion cells with this photopigment.
  • Respond directly to light; no input from rods or cones needed.

The Biochemistry of the Circadian Rhythm

• Key Genes:
  • Two genes responsible for generating the circadian rhythm.
• Period (PER) Gene:
  • Produces PER proteins.
• Timeless (TIM) Gene:
  • Produces TIM proteins.
• PER and TIM Function:
  • Increase activity in SCN neurons, regulating sleep and waking.
• Mutations:
  • Mutations in PER gene lead to odd rhythms or decreased alertness after sleep deprivation.

Melatonin

• SCN Control:
  • SCN influences sleep/wake via other brain areas.
• Pineal Gland Regulation:
  • Regulates pineal gland, which releases melatonin.
• Melatonin's Role:
  • Promotes sleep; rises 2-3 hours before bedtime.
  • Resets circadian clock via SCN receptors.
  • Afternoon melatonin can advance the clock and helps as a sleep aid.

Sleep and Altered States of Consciousness

• Active Brain State:
  • Sleep is actively produced by the brain.
• Characteristics:
  • Moderate decrease in brain activity; decreased response to stimuli.
• Distinctions:
  • Sleep differs from coma, unresponsive wakefulness syndrome, minimally conscious state, and brain death.

Coma

• Definition:
  • Extended unconsciousness with low, steady brain activity.
• Responsiveness:
  • Little response to stimuli.

Unresponsive Wakefulness Syndrome

• State:
  • Alternation between sleep and moderate arousal, but no awareness.
• Arousal:
  • Some autonomic response to pain.
• Activity:
  • No purposeful activity or response to speech.

Minimally Conscious State

• State:
  • Higher than vegetative state; occasional brief purposeful actions and limited speech comprehension.

Brain Death

• Definition:
  • No brain activity and no response to any stimulus.

Stages of Sleep

• Alpha Waves:
  • Present during relaxation.
• Stage 1 Sleep:
  • Sleep has just begun.
  • EEG shows irregular, jagged, low-voltage waves.
  • Brain activity starts to decline.
• Stage 2 Sleep:
  • Characterized by:
    • Sleep spindles (related to memory consolidation)
    • K-complexes

Slow-Wave Sleep (SWS)

• EEG:
  • Slow, large amplitude waves.
• Physiological Changes:
  • Slower heart rate, breathing rate, and brain activity.
• Neuronal Activity:
  • Highly synchronized.

Polysomnograph Records

• Illustrative examples of EEG patterns during:
  • Relaxed wakefulness
  • Stage 1 sleep
  • Stage 2 sleep (with sleep spindle and K-complex)
  • Slow-wave sleep
  • REM sleep

NREM and REM Cycles

• NREM Sleep:
  • Stages other than REM.
• Sleep Progression:
  • Progress through stages 1, 2, then slow-wave sleep.
• Cycle Reversal:
  • After ~1 hour, cycle back from slow-wave to stage 2 and then REM.
• Cycle Length:
  • Each cycle is ~90 minutes.

Sleep Stage Dynamics

• Early Night:
  • Slow-wave sleep predominates.
• Late Night:
  • REM sleep predominates.
• Slow-Wave Sleep Duration:
  • Decreases as the night progresses.
• REM Sleep Duration:
  • Increases as the night progresses.
• Dreaming:
  • Strongly associated with REM, but can occur in other stages.

Brain Mechanisms of Wakefulness and Arousal - Reticular Formation

• Components:
  • Various mechanisms associated with wakefulness and arousal.
• Reticular Formation:
  • From medulla to forebrain; responsible for arousal.

Pontomesencephalon

• Location:
  • Part of the reticular formation in the midbrain; contributes to cortical arousal.
• Axon Projections:
  • Extend to hypothalamus, thalamus, and basal forebrain.
• Neurotransmitters:
  • Releases acetylcholine, glutamate, GABA, or dopamine.
• Effects:
  • Excitatory and inhibitory effects on the cortex.
• Stimulation:
  • Awakens sleeping individuals and increases alertness.

Brain Mechanisms of Wakefulness and Arousal—The Locus Coeruleus

• Location:
  • Small structure in the pons.
• Neurotransmitter:
  • Releases norepinephrine to arouse the cortex and increase wakefulness.
• Activity During Sleep:
  • Usually dormant.

Brain Mechanisms of Wakefulness and Arousal—The Hypothalamus

• Neurotransmitter:
  • Releases histamine for widespread excitatory effects.
• Antihistamines:
  • Cause sleepiness.

Brain Mechanisms of Wakefulness and Arousal—Orexin

• Location:
  • Lateral and posterior nuclei of the hypothalamus.
• Neurotransmitter:
  • Releases orexin (hypocretin).
• Function:
  • Needed to stay awake rather than wake up.
  • Stimulates neurons in the basal forebrain for wakefulness and arousal.
    *Basal Forebrain:
    *Area anterior and dorsal to Hypothalamus

Brain Mechanisms of Sleep and Waking

• Simplified Neural Circuit Diagram:
  • Shows key brain structures (basal forebrain, hypothalamus, dorsal raphe, pontomesencephalon, locus coeruleus).
  • Highlights neurotransmitters (acetylcholine, GABA, histamine, norepinephrine) involved in promoting sleep and wakefulness.

Brain Activity in REM Sleep

• PGO Waves:
  • High-amplitude electrical potentials in pons, lateral geniculate, and occipital cortex.
• REM Sleep Stimulus:
  • Dopamine release in the amygdala.

Sleep and the Inhibition of Brain Activity

• GABA Function:
  • Inhibitory neurotransmitter important for:
    • Decreasing temperature and metabolic rate.
    • Decreasing neuronal stimulation.

Sleep Disorders

• Insomnia:
  • Inadequate sleep due to noise, stress, pain, diet, medication, disorders, substance dependence, or circadian rhythm shifts.

Sleep Apnea

• Definition:
  • Inability to breathe while sleeping for a prolonged time.
• Consequences:
  • Daytime sleepiness, impaired attention, depression, heart problems.
• Causes:
  • Genetics, hormones, old age, obesity, brain mechanism deterioration.
• Effects:
  • Cognitive impairment.

Narcolepsy

• Definition:
  • Sudden daytime sleep attacks.
• Symptoms:
  • Cataplexy (muscle weakness from strong emotion).
  • Sleep paralysis.
  • Hypnagogic hallucinations.
• Cause:
  • Loss of hypothalamic cells producing orexin.
• Biochemical Marker:
  • Only behavioral disorder with a reliable biochemical marker.
• Treatment:
  • Stimulants (e.g., Ritalin) to boost dopamine & norepinephrine.

Periodic Limb Movement Disorder

• Definition:
  • Repeated involuntary movement of legs/arms during sleep.
• Movement Pattern:
  • Legs kick every 20–30 seconds for minutes to hours.
• Occurrence:
  • Usually during NREM sleep.

REM Behavior Disorder

• Definition:
  • Vigorous movement during REM sleep, acting out dreams.
• Dream Content:
  • Frequently defending against attack, leading to:
    • Punching, kicking, leaping.
• Consequences:
  • Injuries to self or others, property damage.

Night Terrors and Sleepwalking

• Night Terrors:
  • Intense fear episodes during NREM sleep.
• Sleepwalking:
  • Common in kids, runs in families, happens in stage 3 or 4; not linked to dreaming; safe to wake a sleepwalker.
• Sexsomnia:
  • Sexual behavior during sleep; can affect relationships.

Functions of Sleep

• Multiple Functions:
  • Resting muscles.
  • Decreasing metabolism.
  • Performing cellular maintenance in neurons.
  • Reorganizing synapses.
  • Strengthening memories.

Sleep and Energy Conservation

• Original Function:
  • Probably to conserve energy.
• Conservation Mechanisms:
  • ~1-2 Celsius degree decrease in body temperature in mammals.
  • Decrease in muscle activity.

Sleep and Memory Enhancement

• Role in Learning:
  • Enhances learning and strengthens memory.
• Performance Improvement:
  • Better performance on new tasks after adequate sleep.
• Brain Activity:
  • Increased activity in brain areas activated during learning while asleep.

Sleep and Memory Consolidation

• Hippocampal Activity:
  • Activity patterns during learning are similar to those during sleep.
  • Suggests brain replays daily experiences during sleep.
• Synaptic Changes:
  • Brain strengthens some synapses and weakens others during sleep.
• Knowledge Storage:
  • Depends on highly synchronized sharp wave ripples transferring information from hippocampus/thalamus to parietal/frontal cortex.
  • Weeding out unsuccessful connections

Functions of REM Sleep

• Time Allocation:
  • Humans spend ~1/3 of life asleep; ~1/5 in REM.
• Species Variation:
  • REM sleep time varies across species (e.g., cats).
  • Positive correlation between REM sleep percentage and total sleep time.
  • Humans with more sleep have higher REM percentage.

REM Sleep Functions

• Inconclusive Research:
  • Exact functions of REM are still being researched.
• Possible Functions:
  • Brain may discard useless connections.
  • Maurice (1998): REM shakes eyeballs for corneal oxygenation.

The Relationship Between Age and REM Sleep for Humans

• Age-Related Sleep Patterns:
  • REM sleep decreases with age

Biological Perspectives on Dreaming

• Research Challenges:
  • Subjects cannot always accurately remember dreams.
• Two Theories:
  • Activation-synthesis hypothesis
  • Neurocognitive hypothesis

The Activation-Synthesis Hypothesis

• Dream Initiation:
  • Dreams start with spontaneous activity in the pons, activating cortex.
• Cortex Synthesis:
  • Cortex synthesizes a story from activation pattern.
• Sensory Integration:
  • Normal sensory information may be integrated, but usually isn't.
• Paralysis:
  • Inability to move during dreams is common.

The Neurocognitive Hypothesis

• Emphasis:
  • Less on pons, PGO waves, REM sleep.
• Dream Similarity:
  • Dreams are similar to thinking under unusual circumstances.
• Stimulation:
  • Dreams start with arousing stimuli generated in the brain.
  • Stimulation is combined with recent memories and senses.

Neurocognitive Hypothesis - Sensory & Motor Aspects

• Sensory Deprivation:
  • Brain gets little information from sense organs, so images generated without constraints.
• Motor Suppression:
  • Arousal cannot lead to action because the primary motor cortex and spinal cord motor neurons are suppressed.
• Prefrontal Cortex Suppression:
  • Impairs working memory during dreaming.

Conditions of Neurocognitive Hypotheses

• High Activity:
  • Inferior parietal cortex (visual-spatial perception).
  • Areas outside V1 (visual imagery).
  • Hypothalamus and amygdala (emotional and motivational content).

The Neurocognitive Hypothesis— Summary

• Stimulation:
  • Internal or external stimulation activates parts of the parietal, occipital, and temporal cortex.
• Dreams without content: “white dreams”
• Hallucinations:
  • Lack of sensory input and prefrontal cortex impairment creates hallucinatory perceptions.

Study Questions

• A list of questions covering various topics from the chapter, including:
  • Endogenous rhythms
  • Biological clock cues
  • Suprachiasmatic nucleus (SCN) role
  • Biochemical basis of circadian rhythm
  • Stages of sleep
  • REM sleep features and control
  • Local sleep control
  • Sleep disorders
  • Functions of sleep
  • Sleep patterns across species
  • Purpose of REM sleep
  • Theories of dreaming