SLEEP, DREAMING, AND CIRCADIAN RHYTHMS

Sleep

is an active biological state involving organized changes in brain activity, physiology, behavior, and consciousness.

Electroencephalogram (EEG)

- A recording of electrical activity produced by the brain.

- It is used to distinguish the different stages of sleep.

Electrooculogram (EOG)

A recording of eye movements that helps identify rapid eye movements associated with REM sleep.

Electromyogram (EMG)

- A recording of muscle activity that helps identify changes in muscle tone during sleep.

- These three measures are the standard psychophysiological measures used to define sleep stages.

Alpha Waves

Relatively regular 8-12 Hz EEG waves associated with relaxed wakefulness.

Stage 1 Sleep

The initial stage of NREM sleep, characterized by a low-voltage, relatively high-frequency EEG.

Stage 2 Sleep

A deeper NREM stage characterized by sleep spindles and K complexes.

Stage 3 Sleep

A deeper sleep stage in which delta waves begin to appear.

Stage 4 Sleep

The deepest traditional NREM stage, characterized by a predominance of delta waves.

REM Sleep

A sleep state characterized by rapid eye movements, low-amplitude high-frequency EEG activity, and loss of tone in the core muscles.

NREM Sleep

The collection of sleep stages that are not REM sleep.

Slow-Wave Sleep (SWS)

Stages 3 and 4 of traditional sleep staging, characterized primarily by slow delta-wave activity.

Dreams recall

- occurs predominantly after awakening from REM sleep.

- do not necessarily occur instantaneously; research indicates that their duration can correspond reasonably well with real time.

REM sleep

is strongly associated with dreaming, but dreaming is not exclusively a REM phenomenon.

Sleep Deprivation

A condition in which an individual obtains substantially less sleep than normally required.

Reduced attention

— difficulty maintaining focused attention.

Impaired executive function

— reduced ability to plan, regulate behavior, and make effective decisions.

Microsleeps

brief episodes of sleep that may occur while a sleep-deprived person appears to remain awake.

Reduced cognitive and physical performance

— Deterioration in performance becomes increasingly evident with prolonged deprivation.

REM-Sleep Deprivation

produces a REM rebound, meaning an increased proportion of REM sleep following deprivation.

Circadian Rhythm

- A biological rhythm that follows an approximately 24-hour cycle.

- Sleep-wake patterns, body temperature, eating, and many other physiological processes display circadian rhythmicity.

Zeitgebers

- Environmental time cues that entrain or synchronize circadian rhythms.

- for mammals is the daily light-dark cycle.

Free-Running Rhythm

A circadian rhythm that continues in the absence of environmental time cues.

Free-Running Period

The duration of a free-running circadian cycle under conditions without zeitgebers.

Internal Desynchronization

A condition in which normally coordinated circadian rhythms become separated and follow different timing patterns.

Shift Work

Circadian disruption produced when work schedules require individuals to remain active or sleep at times that conflict with their natural sleep-wake cycle.

jet lag

Circadian disruption caused by rapid travel across time zones.

Suprachiasmatic Nuclei (SCN)

- Structures located in the medial hypothalamus that function as the major circadian clocks in mammals.

- Damage to the SCN disrupts the normal circadian timing of sleep-wake cycles and other biological rhythms.

Retinohypothalamic Tracts

- Neural pathways carrying information about environmental light from the retina to the SCN.

- They provide an important route through which the light-dark cycle synchronizes the circadian clock.

Melanopsin

A photopigment found in specialized retinal ganglion cells that contributes to the synchronization of circadian rhythms by light.

Circadian Genes

Genes involved in the molecular mechanisms responsible for maintaining biological rhythms.

Tau Gene

A mammalian circadian gene first identified through research on hamsters with unusually short

free-running rhythms.

circadian system

is internally generated but continuously synchronized with environmental cues, particularly light.

Hypothalamus

- Several hypothalamic areas participate in sleep-wake regulation.

- Damage to different regions can produce excessive sleepiness or difficulty sleeping.

Reticular Formation

A brain-stem system involved in maintaining arousal and wakefulness.

Reticular Activating System

The ascending neural system associated with cortical activation and alertness.

Reticular REM-Sleep Nuclei

Brain-stem nuclei involved in producing the physiological characteristics of REM sleep.

Orexin

- A neuropeptide involved in promoting wakefulness.

- Reduced ____ levels and reduced _____-producing neurons are associated with narcolepsy.

Melatonin

- A hormone synthesized from serotonin in the pineal gland.

- Its secretion follows a circadian pattern and is highest during darkness.

- is considered

particularly relevant in this context because it can shift circadian timing.

Chronobiotic

- A substance that adjusts the timing of internal biological rhythms.

Freudian Theory

- Freud proposed that dreams express disguised versions of unacceptable or repressed wishes.

Activation-Synthesis Theories

Hobson's theory proposes that neural activity generated during REM sleep provides largely random signals to the cerebral cortex, which then attempts to synthesize these signals into a meaningful dream experience.

Insomnia

Difficulty initiating or maintaining sleep.

Hypersomnia

Excessive sleep or excessive sleepiness.

Sleep Apnea

Repeated interruptions of breathing during sleep that disrupt normal sleep.

Narcolepsy

A disorder characterized particularly by sudden daytime sleep attacks and abnormal regulation of

REM-related phenomena.

Cataplexy

A sudden loss of muscle tone during wakefulness, often triggered by emotional experiences.

Sleep Paralysis

Temporary inability to move when falling asleep or awakening.

Hypnagogic Hallucinations

Dreamlike experiences that occur during wakefulness, particularly around the transition into sleep.

Hypnotic Drugs

- Drugs used to promote sleep.

- They may be useful for short-term sleep difficulties but can produce problems when used chronically.

Benzodiazepines

- Hypnotic drugs that can reduce sleep latency and increase total sleep time in the short term, but

chronic use can produce tolerance, dependence, altered sleep patterns, and next-day drowsiness.

Antihypnotic Drugs

Drugs that promote wakefulness, often by increasing catecholaminergic activity.

Melatonin Treatment

Exogenous melatonin has a modest sleep-promoting effect according to the chapter, but its more

established role is in adjusting circadian timing.

Monophasic Sleep Cycle

A sleep pattern in which sleep occurs primarily in one consolidated period each day.

Polyphasic Sleep Cycle

A sleep pattern in which daily sleep is divided into multiple periods.

Sleep Inertia

Temporary impairment in alertness and performance immediately after awakening.