Glossary
Activation-Synthesis Theory
A theory suggesting that dreams result from the brain's attempt to make sense of random neural activity during REM sleep.
Example:
According to the Activation-Synthesis Theory, your dream about flying pigs might just be your brain trying to create a narrative from random signals.
Circadian Rhythm
A natural, internal process that regulates the sleep-wake cycle and repeats roughly every 24 hours.
Example:
Your body's natural tendency to feel sleepy around 10 PM and wake up around 6 AM, even without an alarm, is governed by your circadian rhythm.
Consciousness
An individual's awareness of their own thoughts, feelings, actions, and surroundings.
Example:
When you are fully awake and able to respond to a friend's question, you are demonstrating a high level of consciousness.
Consolidation Theory
A theory proposing that dreams, particularly during REM sleep, play a crucial role in processing and strengthening memories.
Example:
After a day of intense studying, your brain might use dreams, as per the Consolidation Theory, to organize and solidify the new information you learned.
Delta Waves
Large, slow brain waves associated with deep, restorative sleep (Stage 3 NREM).
Example:
When a person is in their deepest sleep, an EEG would primarily show the presence of delta waves.
Electroencephalography (EEG)
A neurophysiological measurement technique that records the electrical activity of the brain, often used to study sleep stages.
Example:
Researchers used electroencephalography (EEG) to observe the distinct brain wave patterns of a participant as they transitioned from wakefulness into deep sleep.
Hypnagogic Sensations
Brief, vivid sensory phenomena that occur during the transition from wakefulness to sleep, such as falling or floating sensations.
Example:
Just as he was falling asleep, Mark felt a sudden jolt, a common hypnagogic sensation that made him feel like he was tripping.
Insomnia
A common sleep disorder characterized by persistent difficulty falling asleep, staying asleep, or experiencing non-restorative sleep.
Example:
Despite feeling exhausted, Maria often lies awake for hours, a classic symptom of insomnia.
Jet Lag
A temporary sleep problem caused by traveling across multiple time zones, disrupting the body's natural circadian rhythm.
Example:
After flying from New York to Tokyo, Sarah felt disoriented and struggled to sleep at night, experiencing severe jet lag.
K-complexes
Large, high-amplitude brain waves that occur during Stage 2 NREM sleep, often in response to external stimuli.
Example:
A sudden noise might trigger a K-complex in the brain waves of someone in Stage 2 sleep, even if they don't fully wake up.
Memory Consolidation
The process by which new memories are stabilized and strengthened, moving from short-term to long-term storage, significantly aided by sleep.
Example:
Getting a good night's sleep after learning new material is essential for memory consolidation, helping you remember it for the long term.
Muscle Atonia
A temporary paralysis of the voluntary muscles that occurs during REM sleep, preventing individuals from acting out their dreams.
Example:
The phenomenon of muscle atonia explains why you can't physically run away from a monster in your dream, even if you desperately want to.
NREM Sleep
Non-Rapid Eye Movement sleep, which consists of three distinct stages (N1, N2, N3) characterized by progressively slower brain waves and deeper sleep.
Example:
During the first few hours of the night, most of your sleep is spent in NREM sleep, particularly the deeper stages.
Narcolepsy
A chronic neurological disorder characterized by overwhelming daytime sleepiness and sudden attacks of sleep.
Example:
During a quiet moment in class, John suddenly fell asleep, a symptom consistent with narcolepsy.
REM Rebound
The tendency for individuals to experience increased amounts of REM sleep after periods of REM sleep deprivation.
Example:
After several nights of poor sleep, a student might experience REM rebound, leading to longer and more intense dreams on subsequent nights.
REM Sleep (Rapid Eye Movement Sleep)
A paradoxical sleep stage characterized by rapid eye movements, vivid dreaming, muscle atonia, and brain activity similar to wakefulness.
Example:
During REM sleep, even though your body is largely paralyzed, your brain is highly active, leading to vivid and memorable dreams.
REM Sleep Behavior Disorder (RBD)
A sleep disorder in which individuals physically act out vivid, often unpleasant dreams due to a lack of muscle atonia during REM sleep.
Example:
A person thrashing and yelling during a dream, rather than remaining still, might be experiencing REM Sleep Behavior Disorder (RBD).
Restoration Theory
A theory suggesting that sleep allows the body and brain to repair and rejuvenate themselves, restoring energy and optimal functioning.
Example:
After a strenuous workout, your body relies on sleep, according to the Restoration Theory, to repair muscle tissue and replenish energy stores.
Shift Work
Employment that requires working outside of traditional daytime hours, often leading to disruptions in the natural sleep-wake cycle.
Example:
A nurse who works rotating night shifts often struggles with fatigue and sleep issues due to the demands of shift work.
Sleep Apnea
A serious sleep disorder in which breathing repeatedly stops and starts during sleep, leading to fragmented sleep and reduced oxygen levels.
Example:
Mark's partner often complains about his loud snoring and gasping sounds during the night, which are common indicators of sleep apnea.
Sleep Spindles
Bursts of rapid, rhythmic brain wave activity that appear during Stage 2 NREM sleep.
Example:
The presence of sleep spindles on an EEG indicates that a person has entered Stage 2 of non-REM sleep.
Somnambulism (Sleepwalking)
A sleep disorder characterized by complex behaviors, such as walking or talking, performed while in a state of deep sleep, with no memory of the event.
Example:
During the night, a child might get out of bed and wander around the house, completely unaware, a behavior known as somnambulism.
Stage 1 NREM
The initial, light stage of sleep, serving as a transition between wakefulness and sleep, often accompanied by hypnagogic sensations.
Example:
As you begin to drift off while watching a boring lecture, you might enter Stage 1 NREM, feeling a sudden jerk as if you're falling.
Stage 2 NREM
A deeper stage of sleep characterized by the appearance of sleep spindles and K-complexes on an EEG.
Example:
During Stage 2 NREM, your body temperature drops, heart rate slows, and brain activity shows bursts of rapid, rhythmic brain wave activity.
Stage 3 NREM (Slow-Wave Sleep/Deep Sleep)
The deepest stage of NREM sleep, characterized by high-amplitude, low-frequency delta waves, making it difficult to awaken someone.
Example:
Children often experience a significant amount of Stage 3 NREM, which is crucial for physical growth and restoration.
Suprachiasmatic Nucleus (SCN)
A pair of cell clusters in the hypothalamus that controls the circadian rhythm by responding to light and dark signals.
Example:
Exposure to bright light in the morning helps to reset your suprachiasmatic nucleus (SCN), signaling to your body that it's daytime and time to be awake.