Sleep

PS 101: General Psychology - Sleep, Dreaming, & Consciousness

Biological Rhythms

  • All living things exhibit cycles of activity.

  • Example: Leaves changing color outside are part of a circumannual cycle which affects many plants.

  • Circadian rhythms:

    • Defined as cycles that vary around a 24-hour day.

Our Circadian Rhythms

  • Zeitgebers: Time cues that entrain our circadian rhythms, which can be classified into:

    • Biological cues (e.g., hormone levels)

    • Environmental cues (e.g., light, temperature)

    • Social cues (e.g., work schedule, social interactions)

  • Question posed: What would happen to our circadian rhythm if we had no zeitgebers?

If We Had No Zeitgebers…

  • An experiment involved individuals living in an underground bunker with consistent lighting for several days.

    • Result: Their free-running circadian rhythm was closer to 26 hours.

    • Noted behavior: Participants fell asleep and woke up approximately 2 hours later each consecutive day.

Biological Clocks in the Brain

  • Suprachiasmatic nucleus (SCN) of the hypothalamus:

    • Functions as a biological clock.

    • Positioned just above the optic chiasm, where the optic nerves from each eye cross.

  • Role of SCN:

    • Sends axonal projections to the pineal gland.

    • Pineal gland releases melatonin to regulate sleep-wake cycles.

    • In daylight, SCN inhibits the pineal gland; during decreased daylight, the activity of the pineal gland increases.

Stages of Sleep

  • Sleep is categorized into two primary types:

    • Rapid Eye Movement (REM) sleep

    • Non-Rapid Eye Movement (NREM) sleep

  • Dreaming occurs in both phases, but a greater number of dreams are associated with REM sleep.

  • Rapid eye movements (REM) are not directly linked to dreaming, potentially being a byproduct or overflow of central nervous activity.

Features of REM Sleep

  • During dreaming:

    • Sympathetic nervous system activity increases:

    • Heart rate

    • Breathing

    • Blood pressure

  • Physical state during REM:

    • Eyes move rapidly; however, all other skeletal muscles are paralyzed.

    • Muscle movement inhibition is controlled by the pontine reticular formation in the brain, preventing actions during dreams.

Disorders of REM Sleep

  • REM Sleep Behavior Disorder: In this disorder, the paralysis typically experienced does not function properly, leading individuals to act out their dreams, thrashing in bed or even attacking.

  • Sleep Paralysis: A temporary inability to move or speak that occurs upon waking.

    • Termed Atonia: Meaning inability to move.

Stages of Sleep (NREM)

  • NREM sleep consists of four stages:

    • Stage One: Light sleep; includes:

    • EEG shows theta waves (low amplitude, low frequency of 4-7 cycles per second).

    • Features slow eye movements, irregular breathing, muscle relaxation, and is easy to awaken from.

    • Many might not realize they have fallen asleep.

    • Stage Two: Follows Stage 1; characterized by:

    • Sleep Spindles: Bursts of waves (12-14 cycles per second).

    • K Complexes: High amplitude, low frequency waves that often respond to stimulation (both internal and external).

    • Stage Three: Begins approximately 30-45 minutes after sleep onset, showcasing:

    • An increase in delta waves (high amplitude, low frequency of 0.5-2 cycles per second).

    • Almost no eye movement observed.

    • Stage Four: Deepest sleep stage, characterized by:

    • Greater than 50% delta waves in the EEG, very challenging to wake from.

    • No eye movements observed.

Measuring Sleep Stages

  • Techniques to measure sleep stages:

    • EEG: Electroencephalography for brain wave activity.

    • EMG: Electromyography to measure muscle activity.

    • EOG: Electrooculogram for eye movement tracking.

Wakefulness and Drowsiness on the EEG

  • During wakefulness, EEG displays:

    • Beta waves: Low amplitude and high frequency.

  • In drowsiness, EEG indicates:

    • Alpha waves: Higher amplitude and slower frequency (8-12 cycles per second).

The Full Sleep Cycle

  • A full sleep cycle typically lasts about 90 minutes.

    • Average of approximately 5 cycles per night.

    • The first REM episode may last 5-10 minutes, with subsequent REM cycles lasting up to 45 minutes.

    • REM Rebound: Phenomenon in which sleep-deprived individuals enter REM more quickly and remain longer during it.

Sleep Patterns Change with Age

  • REM sleep decreases as we age:

    • Newborns sleep around 16 hours per day with 50% in REM.

    • Adults in their 20s generally sleep about 8 hours per day with 20% in REM.

    • By ages 60-70, sleep decreases to about 6 hours per day with only 15% in REM, and deep sleep stages significantly decline.

Brain Mechanisms of Sleep: The RAS

  • The Reticular Activating System (RAS):

    • A neuronal pathway extending from the medulla to the thalamus, also known as the reticular formation.

    • Its main role is maintaining wakefulness and alertness.

  • Effects of RAS damage or stimulation:

    • Damage results in decreased activity and increased sleep.

    • Electrical stimulation leads to heightened activity and increased arousal.

Brain Mechanisms of Sleep: The Raphe

  • The Raphe nuclei:

    • A group of neurons producing serotonin, originating in the brainstem, extending through the pons and medulla to the midbrain.

    • Most active during sleep onset, inhibiting the RAS to facilitate sleepiness.

    • Consequences of manipulation:

    • Damage leads to significantly reduced sleep.

    • Stimulation induces sleepiness.

Neurotransmitters that Promote Sleep

  • Serotonin: Released by the raphe nuclei and promotes sleep; however, it is mostly inactive during REM sleep.

  • Adenosine: Another sleep-promoting neurotransmitter; its levels build up throughout the day, inhibiting wakefulness-related acetylcholine neurons.

Hormones that Promote Sleep

  • Melatonin: Hormone released by the pineal gland in response to signals from the SCN.

    • Production is suppressed by light exposure.

    • Impacts circadian rhythms and can aid in sleep onset when taken before bedtime or when adjusting to new time zones.

Neurotransmitters that Promote Arousal

  • Norepinephrine: Main neurotransmitter in the RAS, responsible for wakefulness and alertness.

  • Acetylcholine: Originates in basal forebrain; it serves to enhance wakefulness and activate cortical neurons. However, injecting acetylcholine into the pons can provoke REM sleep.

Sleep Deprivation Studies in Humans

  • A 1970 study documented six individuals who stayed awake for 205 consecutive hours, manifesting:

    • Hallucinations

    • Delusions

    • Double vision

    • Enhanced sensitivity to pain

    • Physiological functions remained relatively unaffected.

  • Recovery occurred after several nights of adequate sleep.

  • Noteworthy fact: The world record for staying awake is 264.4 hours (11 days), set by Randy Gardner in 1964, who subsequently slept for 15 hours and recovered.

Sleep Deprivation Studies in Lab Animals

  • Research included experiments on rats where sleep-deprived ones were monitored with EEG while placed on a rotating disk above water.

    • Lack of sleep required them to remain active to avoid falling into water.

    • Question posed: What do you think happened?

Sleep Deprivation Studies in Lab Animals (Continued)

  • After 33 hours, the sleep-deprived rats began to show severe consequences; all perished by day 32 while control rats survived.

  • Observations include:

    • Scrawny appearance

    • Skin ulcers

    • Elevated food intake

    • Weight loss

    • Decreased body temperature

  • Noted changes in norepinephrine levels.

  • Ethical considerations: These types of studies are generally not conducted nowadays.

Long-Term Effects of Chronic Sleep Deprivation

  • Although direct mortality from sleep deprivation in humans is unproven, sleep deprivation leads to significant health risks:

    • High blood pressure

    • High cholesterol

    • Increased risk of type 2 diabetes

    • Impaired immune system

    • Heightened sensitivity to pain

    • Increased likelihood of Alzheimer's disease

    • Connection to depression and anxiety

    • Notably, receiving less than 7 hours of sleep per night can equate to cognitive impairments akin to being legally intoxicated.

Why Do We Need Sleep?

  • Humans spend approximately 33% of their lives sleeping.

  • Theories regarding the purpose of sleep include:

    • Energy conservation

    • Avoidance of predation

    • Restoration of bodily resources

    • Memory consolidation

    • Most likely, a combination of all these theories holds true.

Sleeping to Conserve Energy

  • Sleeping helps save energy by preventing exhaustion and lowering calorie expenditure.

  • Potential evolutionary advantage: Limiting energy resource usage when food is scarce.

Sleeping to Avoid Predation

  • Sleep patterns have evolved in animals based on their ecological function; humans are nocturnal.

    • Nocturnal beings sleep during the day while many grazing animals only need between 2-4 hours of sleep a day for sufficient foraging.

Sleeping for Restoration

  • Sleep facilitates the restoration of resources depleted during the day and eliminates waste:

    • Data suggests intense physical exercise enhances slow-wave (NREM) sleep.

    • Restoration activity includes:

    • Growth hormone helping in tissue repair.

    • Clearance of metabolic waste from the brain via cerebrospinal fluid, potentially eliminating up to 4.4 lbs annually.

Sleeping for Memory

  • Slow-wave sleep plays a crucial role in:

    • Memory consolidation and long-term storage.

    • Information learned before sleep is remembered more effectively after sleep.

    • Sleep enhances memory performance post-learning; deprivation impairs the ability to form memories and increases susceptibility to false recollections.

    • Notably, the hippocampus is active in neurogenesis (the growth of new neurons) during sleep.

REM Deprivation Studies in Humans

  • Participants deprived of REM sleep displayed:

    • Increased irritability, hostility, anxiety, and aggression,

    • Concentration difficulties.

  • Study outcomes showed: after 7 days of deprivation, participants entered REM sleep immediately upon falling asleep.

    • This caused the experiment to become unmanageable.

REM Deprivation Studies

  • Following deprivation, participants exhibited REM rebound, spending 50% more time in REM compared to their baseline levels.

    • Return to normal levels observed after a few nights.

  • Notably, rats deprived of REM sleep would succumb after 16-50 days.

What is the Purpose of REM?

  • Characteristics of REM sleep include:

    • Temporary paralysis of skeletal muscles.

    • Rapid eye movements.

    • EEG during REM closely resembles waking state.

    • Sleep/wake neurotransmitters behave oppositely during REM:

    • Serotonin becomes inactive while acetylcholine is active.

  • Potential functions of REM may include:

    • Information processing

    • Memory consolidation

    • Emotion processing

    • Preparation for awakening

    • Brain development

    • Expression of repressed desires through dreams.

The Purpose of Dreaming

  • Per psychoanalytical theory, dreams serve as "the road to the unconscious":

    • Freud's theory of dreams:

    • Dreams encapsulate repressed wishes that may not be openly expressed.

    • Manifest content refers to the disguised symbols in dreams, whereas latent content refers to their hidden, true meanings.

Sleep Disorders and Parasomnias

  • Occasional sleep issues are prevalent but do not always indicate a disorder.

  • Estimates suggest that 20-60% of the population may experience some form of sleep disorder:

    • Examples include:

    • Insomnia

    • Sleep apnea

    • Sleep terrors and nightmares

    • Sleepwalking

    • Rarer cases involve specific REM sleep disorders.

Insomnia

  • Symptoms of insomnia encompass:

    • Difficulty initiating sleep

    • Frequent awakenings through the night

    • Early morning waking.

    • Statistics: As many as 40% of adults may face temporary or chronic insomnia, with 60% affected during the COVID-19 pandemic.

Causes of Insomnia

  • Multiple contributors to insomnia include:

    • Stress and emotional disturbances

    • Exposure to high stimulation and blue light from screens at night, which suppresses melatonin production.

    • Substance use, including drugs and alcohol.

Sleep Apnea

  • Classification of sleep apnea includes periods where individuals fail to breathe regularly during sleep:

    • Breathing may halt for seconds to minutes, provoking waking episodes.

    • This cycle can repeat hundreds of times nightly.

    • Treatments range from surgical valve insertion to using a nasal continuous positive airway pressure (nCPAP) machine.

Narcolepsy

  • Narcolepsy is characterized by uncontrollable sleep attacks where individuals may fall asleep suddenly:

    • Duration of attacks can range from minutes to hours.

    • Often includes immediate transitions into REM sleep and loss of muscle tone.

    • Treatment typically involves stimulant medication, but there is no known cure.

Nightmares vs. Sleep Terrors

  • Nightmares: Bad dreams generally occurring in REM sleep

    • Notably vivid, can be repetitive, and often leave lingering memories.

    • Associated with stress and conflict, potentially having genetic predispositions (36-51% heritability).

    • More prevalent among females and can appear throughout the lifespan.

  • Sleep Terrors: More common occurrences during NREM stages (3-4).

    • Typically involve distressing behaviors such as sitting up, crying, or screaming without fully waking.

    • Details of the experience are often forgotten, leaving only a sense of fear.

    • Primarily attributed to stress and fatigue.

Sleep Walking and Talking

  • Sleepwalking: Occurs during stages 3-4 of NREM sleep when muscle paralysis does not occur.

    • Sleepwalkers can navigate surroundings, more prevalent in children, but can be harmful in the elderly.

    • Generally advisable to gently awaken the sleepwalker.

  • Sleep Talking (Somniloquy): A more benign phenomenon that occurs in younger individuals

    • Happens during both NREM and REM sleep, but not officially classified as a disorder.

    • There is minimal evidence that it reveals deeply hidden secrets.

Sleep Eating

  • Sleep-related eating disorder: Involves individuals preparing and consuming food while asleep.

    • Often entails high-calorie food choices without recall of eating.

    • Occurs irrespective of hunger at bedtime.

Hypnosis

  • Defined as an altered state of consciousness characterized by:

    • Deep relaxation and detachment from surroundings.

    • High suggestibility towards the direction given by the hypnotist.

  • Applications of hypnosis include:

    • Treatment for substance use issues.

    • Pain management.

    • Enhancement of repressed memories, although this may lead to creation of false memories.