Sleep Flashcards

Question

What is emotional memory, and how does sleep deprivation affect it?

Answer 1

Key Findings • Emotional Memory Definition: • Emotional memory refers to the ability to encode, store, and recall emotionally significant events. • Sleep, particularly REM sleep, plays a key role in processing and consolidating emotional experiences. • Effects of Sleep Deprivation on Emotional Memory: • Study Setup: • Participants were either sleep-deprived (one night of no sleep) or allowed to sleep before an emotional memory task. • The task involved encoding positive, negative, and neutral words, followed by a recognition test two days later after recovery sleep. • Key Results: • Better retention of emotional (positive & negative) stimuli compared to neutral words in both groups. • Sleep-deprived individuals still retained negative stimuli, but overall memory performance was lower than the control group. • Implications: • Suggests that emotionally charged experiences are prioritized for retention, even in sleep-deprived individuals. • Sleep loss disrupts overall memory formation but preserves emotional content, possibly contributing to heightened emotional reactivity in sleep-deprived states. Key Takeaway • Sleep, especially REM sleep, plays a vital role in consolidating emotional memories. Sleep deprivation impairs general memory processing but preserves emotional memories, which may explain increased emotional sensitivity after sleep loss.

Answer 2

Key Findings • Neuronal Activity Replay: • Patterns of brain activity observed while learning a task during wakefulness are replayed during NREM sleep. • This suggests that the brain “rehearses” learned information, reinforcing memory traces. • Reactivation Studies Using External Cues: • Some studies introduced specific cues (e.g., odors) during learning and later re-exposed participants to the same cue during NREM sleep. • Results showed enhanced memory performance, suggesting that reactivating memories during sleep strengthens consolidation. Key Takeaway • NREM sleep plays a critical role in memory consolidation by “replaying” neural activity from prior learning, and targeted reactivation (e.g., odor cues) can further enhance memory retention.

Answer 3

Key Findings • Study Setup: • Researchers deprived participants of sleep for 35 hours and compared their brain activity to a control group that had normal sleep. • Participants viewed increasingly negative emotional images while undergoing fMRI scans. • Key Results: • In sleep-deprived individuals: • The amygdala (emotion-processing center) showed a +60% increase in reactivity compared to the control group. • The prefrontal cortex, which normally regulates amygdala activity, showed reduced functional connectivity. • Emotional responses were exaggerated and less regulated. • Control group (well-rested participants): • Showed more balanced amygdala activity with stronger prefrontal cortex regulation. • Implications: • Sleep deprivation weakens top-down control from the prefrontal cortex, leading to heightened emotional reactivity. • Explains why sleep-deprived individuals experience stronger negative emotions and mood instability. • Could be relevant for understanding mental health disorders, as sleep disturbances are linked to anxiety, depression, and PTSD. Key Takeaway • Sleep deprivation disrupts the brain’s emotional regulation system, leading to exaggerated amygdala responses and impaired prefrontal control, which may contribute to mood instability and increased emotional sensitivity.

Answer 4

Key Findings • REM sleep plays a crucial role in processing emotional experiences and integrating them into long-term memory. • Disruptions in REM sleep impair emotional regulation, making it harder to process and integrate traumatic memories. • Findings from PTSD and Sleep Studies: • Spoormaker & Montgomery (2008): • REM sleep disruptions are linked to heightened re-experiencing symptoms (e.g., intrusive memories, flashbacks). • Germain (2013) Neuroimaging Studies: • PTSD-related sleep disturbances are associated with: • Hyperactivity in the amygdala (excessive emotional responses). • Reduced prefrontal cortex regulation (weakened emotional control during sleep). • Sleep problems before trauma predict PTSD severity: • Individuals with poor sleep before a traumatic event are more likely to develop severe PTSD symptoms. • Interrupting REM sleep after trauma is linked to later PTSD development. Key Takeaway • REM sleep is essential for emotional processing and trauma integration. Disruptions in REM sleep can exacerbate PTSD symptoms by increasing emotional reactivity and impairing memory regulation, making sleep a critical factor in trauma recovery.

Answer 5

Key Findings • Cellular Explanation for Sleep Function: • Sleep is essential for synaptic homeostasis—the balance between synaptic strengthening and weakening. • Studies suggest that synapses are strengthened during wakefulness (due to learning and experience) and then scaled back during sleep, preserving only the most relevant connections. • Sleep allows for protein synthesis, synaptic remodeling, and removal of metabolic waste, preventing neuronal overload. • The Sleepy Mutation (Sik3 Mutation in Mice): • Researchers screened over 8,000 mice and identified one with excessive sleep duration (~15 hours/day) due to a mutation in the Sik3 gene. • The mutation led to hyperphosphorylation of synaptic proteins, increasing the need for sleep. • Similar hyperphosphorylation occurs in sleep-deprived wild-type mice, suggesting that waking experiences increase synaptic phosphorylation, and sleep helps reverse this process. • Supports the idea that sleep regulates synaptic strength and prevents excessive accumulation of synaptic proteins. Key Takeaway • Sleep is crucial for synaptic homeostasis, allowing the brain to prune unnecessary connections and consolidate important ones. The Sleepy mutation (Sik3) supports this by showing that excess synaptic phosphorylation increases sleep need, linking sleep to cellular regulation and neural efficiency.

Answer 6

Key Findings Sleep is controlled by four major interacting neural systems: 1. Forebrain System (Basal Forebrain) – Induces Slow-Wave Sleep (SWS) • The basal forebrain (BF, 基底前脑) promotes SWS (Stage 3 deep sleep) by releasing GABA, which inhibits wake-promoting regions. • Lesions in the basal forebrain reduce SWS, leading to sleep disturbances. 2. Brainstem System (Reticular Formation) – Maintains Wakefulness • The reticular formation (网状结构) in the brainstem helps maintain arousal and wakefulness. • Lesions in this area cause persistent sleep-like states, showing its role in wakefulness. 3. Pontine System (Pons, Subcoeruleus) – Controls REM Sleep • The subcoeruleus (下蓝斑核) in the pons triggers REM sleep and associated phenomena like rapid eye movements and muscle atonia. • Lesions in the subcoeruleus cause REM sleep without atonia, allowing animals to act out dreams. 4. Hypothalamic System (Hypothalamus) – Coordinates Sleep-Wake Regulation • The hypothalamus (下丘脑), particularly the tuberomammillary nucleus (TMN) and lateral hypothalamus, releases hypocretin (orexin) to stabilize sleep-wake states. • Hypocretin deficiency is linked to narcolepsy, a disorder causing sudden sleep attacks. Key Takeaway • Sleep regulation relies on four key neural systems: • Basal forebrain (induces SWS) • Reticular formation (maintains wakefulness) • Subcoeruleus in the pons (triggers REM sleep) • Hypothalamus (stabilizes and regulates transitions between states) • These systems interact dynamically to control the sleep-wake cycle.

Answer 7

Key Findings • Transection studies involve cutting specific brain regions to study their role in sleep and wakefulness. • Bremer’s Classic Experiments (1930s): • Cerveau isolé (Isolated Forebrain) Transection: • Cut at the midbrain level, separating the forebrain from the brainstem. • Result: The animal remained in continuous SWS (slow-wave sleep), showing that the forebrain can generate deep sleep but wakefulness requires brainstem input. • Encéphale isolé (Isolated Brain) Transection: • Cut at the medulla level, separating the brainstem from the spinal cord. • Result: Normal sleep-wake cycles persisted, proving that the essential sleep-wake control structures are above the medulla (in the midbrain and pons). • Key Contribution of Brain Regions to Sleep: • Everything above the medulla contributes to sleep regulation. • The forebrain generates SWS (Stage 3 deep sleep). • The reticular formation in the brainstem is necessary for wakefulness. • The pons (subcoeruleus region) controls REM sleep and muscle atonia. Key Takeaway • Transection studies confirmed that sleep regulation depends on brain regions above the medulla, with the forebrain generating SWS, the brainstem maintaining wakefulness, and the pons controlling REM sleep.

Answer 8

General Sleep Disorders: 1. Insomnia (失眠症) – Difficulty falling asleep, staying asleep, or waking too early. 2. Sleep Apnea (睡眠呼吸暂停症) – Breathing interruptions during sleep, leading to poor sleep quality and excessive daytime sleepiness. • Obstructive Sleep Apnea (OSA) – Caused by airway collapse. • Central Sleep Apnea – Due to the brain failing to send proper signals to breathing muscles. 3. Narcolepsy (嗜睡症) – Sudden, uncontrollable sleep episodes during the day, often linked to hypocretin (orexin) deficiency. 4. REM Behavior Disorder (RBD, REM行为障碍) – Lack of muscle atonia during REM sleep, leading to acting out dreams. 5. Parasomnias (睡眠异常行为) – Unusual behaviors during sleep, including nightmares, sleepwalking, and night terrors. ⸻ Sleep Disorders in Children: 1. Night Terrors (夜惊) – • Occur during NREM Stage 3 (deep sleep, not REM nightmares). • The child screams, appears terrified, but remains unresponsive and does not recall the event. 2. Sleepwalking (梦游症) – • Also occurs during NREM Stage 3, when the child is in deep sleep. • The child may walk or perform activities without conscious awareness. 3. Bedwetting (夜遗尿, Nocturnal Enuresis) – • Often linked to delayed bladder control development. • Usually resolves with age as the nervous system matures. 4. Obstructive Sleep Apnea (OSA) in Children – • Caused by enlarged tonsils or adenoids, leading to breathing interruptions. • Can result in daytime attention problems (mimicking ADHD). Key Takeaway • Sleep disorders range from insomnia and breathing-related issues (apnea) to movement disorders (narcolepsy, RBD) and parasomnias (sleepwalking, night terrors). • Children are more prone to parasomnias like sleepwalking, night terrors, and bedwetting, which often resolve with age but can impact sleep quality.

Answer 9

Key Findings Mechanism (原理) • GABA Agonists: Enhance GABA_A receptor activity, increasing inhibition in the brain. • Benzodiazepines (如Valium, Ativan): Induce sleep but reduce SWS and REM, causing next-day drowsiness. • Z-drugs (如Ambien, Sonata): More selective, promoting sleep with fewer residual effects. • Orexin Receptor Antagonists (如Suvorexant): Block wake-promoting orexin, preventing insomnia without GABAergic side effects. Effects ✔ Short-term benefits: Faster sleep onset, increased sleep time. ❌ Negative effects: • Reduced SWS & REM → Weaker memory consolidation. • Next-day grogginess & cognitive impairment. • Risk of tolerance, dependence, and withdrawal with long-term use. Key Takeaway • Sleeping pills suppress wakefulness or enhance GABAergic inhibition, but long-term use disrupts sleep architecture and increases dependence risk. Best used short-term.

Answer 10

Key Findings 1. Wakefulness • EEG: Beta waves (15–30 Hz) → low-amplitude, high-frequency, desynchronized activity. • Features: Brain is active, ready for processing external stimuli. 2. NREM Stage 1 (Light Sleep, Drowsy State) • EEG: Theta waves (4–7 Hz). • Features: Transition from wakefulness to sleep; somewhat awake, drowsy. 3. NREM Stage 2 (Intermediate Sleep) • EEG: Theta waves, with distinctive: • K-complexes → Large-amplitude, single high-voltage spikes. • Sleep spindles → High-frequency (12–16 Hz), small-amplitude bursts, linked to memory consolidation. • Features: Sleep becomes more stable, reduced responsiveness to external stimuli. 4. NREM Stage 3 (Slow-Wave Sleep, SWS, Deep Sleep) • EEG: Delta waves (<4 Hz, low frequency, high amplitude, synchronized activity). • Features: • Deepest sleep, hardest to wake up from. • Essential for restoration and memory processing. 5. REM Sleep (Paradoxical Sleep) • EEG: Beta waves, similar to wakefulness. • Features: • Brain looks awake, but the body is paralyzed (muscle atonia). • Rapid eye movements (EOG detects eye ball movement under closed eyelids). • Often followed by brief wakefulness before the next sleep cycle. Key Takeaway • Sleep progresses through cycles (~90 min each), transitioning from NREM (Stages 1–3) to REM. • Stage 2 is marked by K-complexes and spindles (linked to memory), Stage 3 is deep sleep (SWS, delta waves, big amplitude, low frequency), and REM mimics wakefulness (beta waves, rapid eye movement, muscle atonia).

Answer 11

Key Findings • Dreaming can occur in all sleep stages, but most vivid and frequent dreams happen during REM sleep. • Brain activity during sleep: • Occipital lobe (visual processing area) is highly active, contributing to vivid and immersive dream content. • Frontal lobe (responsible for logical thinking and reasoning) is less active, which may explain why dreams often lack logical structure. • Night Terrors: • Occur during Stage 3 (Slow-Wave Sleep, SWS), not during REM sleep. • Involves sudden fear, screaming, or panic, but the individual is unresponsive and does not recall the episode upon waking. • More common in children and tend to disappear with age. Key Takeaway • REM sleep produces vivid dreams due to high occipital lobe activation and reduced frontal lobe involvement, making dreams visual but often illogical. • Night terrors are different from nightmares—they occur during deep sleep (Stage 3, SWS), are not dream-related, and often involve intense fear reactions without memory of the event.

Answer 12

Key Findings 1. Memory Consolidation • Sleep strengthens learning and memory retention, especially for motor skills and spatial navigation. • Supporting evidence: • Motor learning studies → People who sleep after practicing a task (e.g., key press sequence) perform better the next day. • Mouse Maze Study → Mice that slept after learning a maze showed improved navigation, suggesting sleep consolidates spatial memory. 2. Restoration and Waste Clearance • Sleep is essential for physical and neural restoration. • Supporting evidence: • Sleep deprivation studies → Mice and humans die if completely sleep-deprived, showing sleep is necessary for survival. • Glial Flushing Hypothesis → During sleep, the glymphatic system (glial cells and cerebrospinal fluid) flushes out toxic waste, including beta-amyloid, which is associated with Alzheimer’s disease. • Sleep statistics → People who sleep 6 hours or less per night have a higher mortality risk compared to those who get 7+ hours. 3. Niche Adaptation (Ecological Perspective) • Sleep helps animals adapt to their ecological niche by keeping them inactive during times of high risk. • Supporting evidence: • Nocturnal and diurnal species evolved sleep patterns to avoid predators. • Animals that are vulnerable during sleep tend to sleep less or in protected environments. 4. Energy Conservation Hypothesis • Sleep reduces metabolic demands, allowing energy savings during periods of inactivity. • Supporting evidence: • Small animals (e.g., bats, rodents) sleep longer because they have higher metabolic rates and need more recovery. • Sleep helps lower body temperature and metabolic activity, reducing energy consumption when food is scarce. Key Takeaway • Sleep is essential for memory consolidation (learning and spatial tasks), restoration (glial flushing and repair), niche adaptation (predator avoidance), and energy conservation (metabolic efficiency), with strong support from sleep deprivation, neurophysiological, and ecological studies.