Week 5 Lecture Content (Sleep I) Flashcards
For the purposes of PSYC317, how do we define sleep? How does this relate to being drowsy?
Source: Lecture 13, Section “Defining Sleep and Drowsiness”
- PSYC317 definition: “A state of diminished sensory responsivity, which follows specific patterns of nervous system activity.”
- Drowsiness is defined as “a state of heightened desire for sleep,” motivating the behaviour of sleep.
- Traditional dictionary definitions insufficient, claiming nervous system inactivity or using vague terms like “powers of the body being restored.”
- PSYC317’s definition focuses on observable changes in sensory responsivity and brain activity during sleep.
- Sleep involves diminished response to external stimuli, but not a complete shutdown of sensory inputs.
Quote: “Drowsiness prompts you to sleep. So our PSYC317 sleep definition is going to be a state of diminished sensory responsivity, which follows specific patterns of nervous system activity.” Source: Lecture 13, Section “Defining Sleep and Drowsiness”
Describe the following stages of the sleep cycle in terms of EEG characteristics and any unique outward features: Stage 1, Stage 2, Stage 3/4 (SWS), and REM. Make sure you are familiar with the R&K method, and the later AASA classification.
Rechtschaffen and Kales (R&K) Method (1968)
Stage 1:
EEG: Dominated by theta waves (4-8 Hz).
Outward features: Light sleep, reduced muscle tone, and possible hypnic jerks (sudden muscle twitches).
Duration: Shortest stage (~10 minutes).
Stage 2:
EEG: Marked by sleep spindles (bursts of 12-14 Hz activity) and K-complexes (large waveforms).
Outward features: Slightly deeper sleep, reduced responsiveness to external stimuli.
Duration: About 15-20 minutes.
Stage 3 & 4 (Slow Wave Sleep - SWS):
EEG: Transition to delta waves (0.5-4 Hz) in Stage 3, with Stage 4 being predominantly delta activity.
Outward features: Deep sleep, least responsive to external stimuli, difficult to awaken. Grogginess if woken from SWS.
Duration: Longest in the first half of the night, gradually decreasing.
These stages are crucial for brain rest and memory consolidation.
REM Sleep:
EEG: Resembles wakefulness, with theta and beta waves (13-32 Hz).
Outward features: Atonia (muscle paralysis except for the eyes), vivid dreaming, rapid eye movements.
Duration: ~20 minutes, with REM periods lengthening throughout the night.
American Academy of Sleep Medicine (AASM) Classification (2007)
Non-REM Stage 1 (N1):
Similar to R&K Stage 1 with theta waves (~10 minutes), some hypnic jerks, and light sleep.
Non-REM Stage 2 (N2):
Same as R&K Stage 2, marked by K-complexes and sleep spindles. Most of the night is spent in N2 (~50%).
Non-REM Stage 3 (N3):
Combines R&K Stages 3 and 4, referred to as SWS. Dominated by delta waves and important for memory consolidation and physical recovery.
REM Sleep (R):
Same as in the R&K method, with high brain activity resembling wakefulness and muscle paralysis. Dreaming is most vivid during REM.
Key Differences Between R&K and AASM:
The AASM system combined Stage 3 and 4 into a single stage (N3) due to the similarities in delta wave activity between these stages.
The AASM system introduced the more formal designation of NREM (N1, N2, N3) and REM (R) sleep, streamlining the classification system and emphasising the importance of each stage in the sleep cycle.
Quote: “By the time you get to Stage 4… it’s predominantly those slow delta waves that you’re seeing… REM sleep, on the other hand, is a kind of paradox because the brain waves look similar to when you’re awake, but you’re asleep and completely paralysed.”
Describe Stage 1 of the sleep cycle in terms of EEG characteristics and any unique outward features.
Make sure you are familiar with the R&K method, and the later AASA classification.
Rechtschaffen and Kales (R&K) Method (1968)
Stage 1:
EEG: Dominated by theta waves (4-8 Hz).
Outward features: Light sleep, reduced muscle tone, and possible hypnic jerks (sudden muscle twitches).
Duration: Shortest stage (~10 minutes).
American Academy of Sleep Medicine (AASM) Classification (2007)
Non-REM Stage 1 (N1):
Similar to R&K Stage 1 with theta waves (~10 minutes), some hypnic jerks, and light sleep.
Describe Stage 2 of the sleep cycle in terms of EEG characteristics and any unique outward features.
Make sure you are familiar with the R&K method, and the later AASA classification.
Rechtschaffen and Kales (R&K) Method (1968)
Stage 2:
EEG: Marked by sleep spindles (bursts of 12-14 Hz activity) and K-complexes (large waveforms).
Outward features: Slightly deeper sleep, reduced responsiveness to external stimuli.
Duration: About 15-20 minutes.
American Academy of Sleep Medicine (AASM) Classification (2007)
Non-REM Stage 2 (N2):
Same as R&K Stage 2, marked by K-complexes and sleep spindles. Most of the night is spent in N2 (~50%).
Describe Stage 3/4 (SWS) of the sleep cycle in terms of EEG characteristics and any unique outward features.
Make sure you are familiar with the R&K method, and the later AASA classification.
Rechtschaffen and Kales (R&K) Method (1968)
Stage 3 & 4 (Slow Wave Sleep - SWS):
EEG: Transition to delta waves (0.5-4 Hz) in Stage 3, with Stage 4 being predominantly delta activity.
Outward features: Deep sleep, least responsive to external stimuli, difficult to awaken. Grogginess if woken from SWS.
Duration: Longest in the first half of the night, gradually decreasing.
These stages are crucial for brain rest and memory consolidation.
American Academy of Sleep Medicine (AASM) Classification (2007)
Non-REM Stage 3 (N3):
Combines R&K Stages 3 and 4, referred to as SWS. Dominated by delta waves and important for memory consolidation and physical recovery.
Describe REM of the sleep cycle in terms of EEG characteristics and any unique outward features.
Make sure you are familiar with the R&K method, and the later AASA classification.
Rechtschaffen and Kales (R&K) Method (1968)
REM Sleep:
EEG: Resembles wakefulness, with theta and beta waves (13-32 Hz).
Outward features: Atonia (muscle paralysis except for the eyes), vivid dreaming, rapid eye movements.
Duration: ~20 minutes, with REM periods lengthening throughout the night.
American Academy of Sleep Medicine (AASM) Classification (2007)
REM Sleep (R):
Same as in the R&K method, with high brain activity resembling wakefulness and muscle paralysis. Dreaming is most vivid during REM.
Describe the key differences Between R&K and AASM:
Key Differences Between Rechtschaffen and Kales (R&K) Method (1968) and American Academy of Sleep Medicine (AASM) Classification (2007):
- The AASM system combined Stage 3 and 4 into a single stage (N3) due to the similarities in delta wave activity between these stages.
- The AASM system introduced the more formal designation of NREM (N1, N2, N3) and REM (R) sleep, streamlining the classification system and emphasising the importance of each stage in the sleep cycle.
Describe Stage 1 of the sleep cycle in terms of EEG characteristics and any unique outward features.
Stage 1:
EEG: Dominated by _____ waves (__ - __ Hz).
Outward features: _____ sleep, _____ muscle tone, and possible ____ (sudden muscle twitches).
Duration: _____ stage (~___ minutes).
theta waves (4-8 Hz).
Light sleep, reduced muscle tone, and possible hypnic jerks
Shortest stage (~10 minutes).
Describe Stage 2 of the sleep cycle in terms of EEG characteristics and any unique outward features.
Stage 2:
EEG: Marked by sleep ______ (bursts of __ - __ Hz activity) and _________ (large waveforms).
Outward features: Slightly _____ sleep, _____ responsiveness to external stimuli.
Duration: About __ - __ minutes.
Stage 2:
EEG: Marked by sleep spindles (bursts of 12-14 Hz activity) and K-complexes (large waveforms).
Outward features: Slightly deeper sleep, reduced responsiveness to external stimuli.
Duration: About 15-20 minutes.
Describe Stage 3/4 (SWS) of the sleep cycle in terms of EEG characteristics and any unique outward features.
Stage 3 & 4 (Slow Wave Sleep - SWS):
EEG: Transition to ____ waves (__ - __ Hz) in Stage 3, with Stage 4 being predominantly ____ activity.
Outward features: ___ sleep, ____ responsive to external stimuli, ____ to awaken. ______ if woken from SWS.
Duration: ______ in the first half of the night, gradually _____.
These stages are crucial for ____ ____ and ____ ____.
Stage 3 & 4 (Slow Wave Sleep - SWS):
EEG: Transition to delta waves (0.5-4 Hz) in Stage 3, with Stage 4 being predominantly delta activity.
Outward features: Deep sleep, least responsive to external stimuli, difficult to awaken. Grogginess if woken from SWS.
Duration: Longest in the first half of the night, gradually decreasing.
These stages are crucial for brain rest and memory consolidation.
Describe REM of the sleep cycle in terms of EEG characteristics and any unique outward features.
REM Sleep:
EEG: Resembles ______, with ____ and ____ waves (__ - __ Hz).
Outward features: _____ (muscle paralysis except for the eyes), vivid dreaming, rapid eye movements.
Duration: ~__ minutes, with REM periods ______ throughout the night.
wakefulness, with theta and beta waves (13-32 Hz).
Atonia
~20 minutes; lengthening
How do K-complexes relate to diminished sensory responsivity? Use sound as an example stimulus, and explain what these EEG events represent in terms of communication between the thalamus and the cortex.
- K-complexes are EEG events in Stage 2 that reflect the brain’s inhibition of sensory inputs.
- In response to stimuli like sound, inhibitory neurons in the thalamus send signals to the cortex, preventing the sound from waking the sleeper.
- This activity serves to keep you asleep while also processing and potentially consolidating memories.
- K-complexes are believed to protect ongoing memory consolidation from being disrupted by external stimuli.
Quote: “K-complexes are being generated by cells projecting from the thalamus to the auditory cortex… They send a signal to the cortex saying, shut up. Stay calm. Don’t wake up.”
Source: Lecture 13, Section “K-complexes”
K-complexes are ___ events in Stage ___ that reflect the brain’s inhibition of sensory inputs.
In response to stimuli like sound, ____ neurons in the ____ send signals to the cortex, preventing the sound from waking the sleeper.
This activity serves to keep you asleep while also processing and potentially consolidating memories.
K-complexes are believed to protect ____ ____ ____ from being disrupted by external stimuli.
K-complexes are EEG events in Stage 2 that reflect the brain’s inhibition of sensory inputs.
In response to stimuli like sound, inhibitory neurons in the thalamus send signals to the cortex, preventing the sound from waking the sleeper.
This activity serves to keep you asleep while also processing and potentially consolidating memories.
K-complexes are believed to protect ongoing memory consolidation from being disrupted by external stimuli.
_____ _____ are EEG events in Stage 2 that reflect the brain’s inhibition of sensory inputs.
In response to stimuli like _____, inhibitory neurons in the thalamus send signals to the cortex, preventing the sound from waking the sleeper.
This activity serves to keep you asleep while also processing and potentially consolidating memories.
____ _____ are believed to protect ongoing memory consolidation from being disrupted by external stimuli.
K-complexes are EEG events in Stage 2 that reflect the brain’s inhibition of sensory inputs.
In response to stimuli like sound, inhibitory neurons in the thalamus send signals to the cortex, preventing the sound from waking the sleeper.
This activity serves to keep you asleep while also processing and potentially consolidating memories.
K-complexes are believed to protect ongoing memory consolidation from being disrupted by external stimuli.
What are sleep spindles and sharp wave ripples? What are the two theoretical ways in which sleep spindles could aid consolidation?
- Sleep spindles: Short bursts of high-frequency waves (12-14 Hz) that co-occur with sharp wave ripples in the hippocampus during non-REM sleep.
- Sharp wave ripples: Hippocampal activity representing replayed memories during sleep.
- Two theories for spindles’ role in memory consolidation:
1. Cortical reactivation: Sleep spindles reactivate cortical cells involved in encoding the memory, strengthening their connections.
2. Inhibitory protection: Spindles may inhibit cortical signals, protecting hippocampal replay from interference.
Quote: “The other theory is that we’re talking about something a little bit like the K-complexes, where… sleep spindles reflect just the scrambling of cortical signals that would otherwise interfere with hippocampal replay.” Source: Lecture 13, Section “Sleep Spindles”
Sleep spindles: Short bursts of ___-frequency waves (__ - __ Hz) that co-occur with sharp wave ripples in the ______ during _____ sleep.
Sharp wave ripples: ________ activity representing replayed memories during sleep.
Two theories for spindles’ role in memory consolidation:
- _____ _____: Sleep spindles reactivate cortical cells involved in encoding the memory, strengthening their connections.
- _____ _____: Spindles may inhibit cortical signals, protecting hippocampal replay from interference.
Sleep spindles: Short bursts of high-frequency waves (12-14 Hz) that co-occur with sharp wave ripples in the hippocampus during non-REM sleep.
Sharp wave ripples: Hippocampal activity representing replayed memories during sleep.
Two theories for spindles’ role in memory consolidation:
1. Cortical reactivation: Sleep spindles reactivate cortical cells involved in encoding the memory, strengthening their connections.
2. Inhibitory protection: Spindles may inhibit cortical signals, protecting hippocampal replay from interference.
How do sleep spindles and delta waves interact and affect our memories? (No need to be detailed with the methods of the study that was presented, just be aware of the specific interactions that were discussed, and their consequences.)
- Delta waves are slow oscillations (0.5-4 Hz) during deep sleep.
- When sleep spindles occur on top of slow delta waves, they help consolidate memories.
- If spindles coincide with less pronounced delta waves (not slow oscillations), memories may be weakened instead of strengthened.
Quote: “Consolidation of memories requires very precise timing between spindles and large amplitude, slow delta oscillations.” Source: Lecture 13, Section “Delta Waves and Spindles in Memory Consolidation”
Delta waves are slow oscillations (__ - __ Hz) during ___ sleep.
When ____ ____ occur on top of slow delta waves, they help consolidate _______.
If _____ coincide with less pronounced delta waves (not slow oscillations), ______ may be weakened instead of strengthened.
Delta waves are slow oscillations (0.5-4 Hz) during deep sleep.
When sleep spindles occur on top of slow delta waves, they help consolidate memories.
If spindles coincide with less pronounced delta waves (not slow oscillations), memories may be weakened instead of strengthened.
____ waves are slow oscillations (0.5-4 Hz) during deep sleep.
When sleep spindles occur on top of slow ___ waves, they help consolidate ______.
If spindles coincide with less pronounced ____ waves (not slow oscillations), ______ may be weakened instead of strengthened.
Delta
delta; memories.
delta; memories
Is the nervous system “inactive” during sleep? Explain. Be sure to consider the different stages of sleep, as well as consider the CNS and PNS.
- The nervous system is not inactive during sleep; it’s just in different states based on sleep stages.
- Slow-wave sleep (SWS) features slower neural activity but is crucial for brain “rest” and recovery. Sleep stages differ in EEG activity, from slow oscillations in SWS to high-frequency beta waves during REM.
- REM sleep has high brain activity, comparable to wakefulness, especially in the motor and visual cortices.
- Peripheral nervous system (PNS) involvement in sleep can be observed in changes in heart rate and respiration, particularly during REM sleep.
- REM sleep causes muscle paralysis (except for eye muscles), meaning the body is inactive, but brain activity is high.
Quote: “Slow-wave sleep is critical for what we might call brain rest…and you get this kind of rebound effect where you try to recuperate slow wave sleep the next time you fall asleep.” Source: Lecture 15, Section “SWS and brain rest”
Is the nervous system “inactive” during sleep?
The nervous system is not inactive during sleep; it’s just in different states based on sleep stages.
Explain what happens to the nervous system during Slow-wave sleep (SWS) sleep?
Slow-wave sleep (SWS) features slower neural activity but is crucial for brain “rest” and recovery.
Explain what happens to the nervous system during REM sleep?
REM sleep has high brain activity, comparable to wakefulness, especially in the motor and visual cortices.
REM sleep causes muscle paralysis (except for eye muscles), meaning the body is inactive, but brain activity is high.
How can the peripheral nervous system (PNS) involvement in sleep be observed?
Peripheral nervous system (PNS) involvement in sleep can be observed in changes in heart rate and respiration, particularly during REM sleep.
Peripheral nervous system (PNS) involvement in sleep can be observed in changes in ________ and _______, particularly during REM sleep.
Peripheral nervous system (PNS) involvement in sleep can be observed in changes in heart rate and respiration, particularly during REM sleep.
Compare and contrast the recuperation theory of sleep vs. the adaptation theory of sleep.
- Recuperation theory: Proposes that sleep is necessary to restore some physiological or neurological function depleted during wakefulness. This could be related to brain homeostasis, energy, or learning.
- Adaptation theory: Suggests sleep is an evolutionary adaptation to conserve energy and avoid dangers, such as predation. Sleep is seen as a protective mechanism rather than restorative.
- Criticism of adaptation theory: Sleep isn’t merely about energy conservation because different sleep stages (e.g., REM) have distinct functions not explained by the need for energy conservation.
- In both theories, slow-wave sleep is highlighted for its homeostatic function, particularly in restoring brain activity.
Quote: “If it was just trying to conserve energy, then that doesn’t really make sense. You’d have these different sleep stages, for example.” Source: Lecture 14, Section “Recuperation and adaptation theories”
________ theory proposes that sleep is necessary to restore some physiological or neurological function depleted during wakefulness. This could be related to brain homeostasis, energy, or learning.
Recuperation theory
________ theory suggests sleep is an evolutionary adaptation to conserve energy and avoid dangers, such as predation. Sleep is seen as a protective mechanism rather than restorative.
Adaptation theory
Recuperation theory of sleep vs. the adaptation theory of sleep - In both theories, _____ sleep is highlighted for its homeostatic function, particularly in restoring brain activity.
Recuperation theory of sleep vs. the adaptation theory of sleep - In both theories, slow-wave sleep is highlighted for its homeostatic function, particularly in restoring brain activity.
Criticism of adaptation theory of sleep?
Sleep isn’t merely about energy conservation because different sleep stages (e.g., REM) have distinct functions not explained by the need for energy conservation.
What is the SHY (Synaptic Homeostasis Hypothesis)? What evidence was discussed in favour of/against this hypothesis?
- SHY hypothesis (Tononi & Cirelli, 2006): Suggests that synapses grow stronger during wakefulness due to learning and experience. During sleep, especially slow-wave sleep, synaptic strength is “downscaled” to prevent saturation.
- Synaptic downscaling: Ensures that there’s enough capacity for learning the next day by reducing synaptic strength during SWS.
- Evidence: Delta wave power reduces over the course of SWS as synapses weaken. Experiments show a reduction in the size of dendritic spines during sleep.
- Some contradictory evidence suggests that not all synapses weaken during sleep. Certain neurons, such as those in the thalamus, might actually increase their synaptic strength during sleep.
Quote: “Sleep is the price we pay for plasticity. As synapses strengthen during the day, they weaken during sleep to free up space for learning the next day.” Source: Lecture 14, Section “SHY Hypothesis”
The ____ hypothesis suggests that synapses grow stronger during wakefulness due to learning and experience. During sleep, especially slow-wave sleep, synaptic strength is “downscaled” to prevent saturation.
SHY hypothesis (Tononi & Cirelli, 2006) suggests that synapses grow stronger during wakefulness due to learning and experience. During sleep, especially slow-wave sleep, synaptic strength is “downscaled” to prevent saturation.
SHY hypothesis (Tononi & Cirelli, 2006) suggests that synapses grow _____ during wakefulness due to learning and experience. During sleep, especially ____ sleep, synaptic strength is “downscaled” to prevent saturation.
SHY hypothesis (Tononi & Cirelli, 2006) suggests that synapses grow stronger during wakefulness due to learning and experience. During sleep, especially slow-wave sleep, synaptic strength is “downscaled” to prevent saturation.
What is synaptic downscaling?
Synaptic downscaling ensures that there’s enough capacity for learning the next day by reducing synaptic strength during SWS.
What is the contradictory evidence to the SHY (Synaptic Homeostasis Hypothesis)?
Some contradictory evidence suggests that not all synapses weaken during sleep. Certain neurons, such as those in the thalamus, might actually increase their synaptic strength during sleep.
Some contradictory evidence to the SHY (Synaptic Homeostasis Hypothesis) suggests that _____________. Certain neurons, such as those in the thalamus, might actually _____ their synaptic strength during sleep.
Some contradictory evidence to the SHY (Synaptic Homeostasis Hypothesis) suggests that not all synapses weaken during sleep. Certain neurons, such as those in the thalamus, might actually increase their synaptic strength during sleep.
What is the evidence to support the SHY (Synaptic Homeostasis Hypothesis)?
Delta wave power reduces over the course of SWS as synapses weaken. Experiments show a reduction in the size of dendritic spines during sleep.
The evidence to support the ___ hypothesis states that delta wave power reduces over the course of SWS as synapses weaken. Experiments show a reduction in the size of dendritic spines during sleep.
The evidence to support the SHY hypothesis (Synaptic Homeostasis Hypothesis) states that delta wave power reduces over the course of SWS as synapses weaken. Experiments show a reduction in the size of dendritic spines during sleep.
The evidence to support the SHY hypothesis (Synaptic Homeostasis Hypothesis) states that ____ wave power reduces over the course of SWS as synapses weaken. Experiments show a _____ in the size of dendritic spines during sleep.
The evidence to support the SHY hypothesis (Synaptic Homeostasis Hypothesis) states that delta wave power reduces over the course of SWS as synapses weaken. Experiments show a reduction in the size of dendritic spines during sleep.
The evidence to support the SHY hypothesis (Synaptic Homeostasis Hypothesis) states that delta wave power reduces over the course of ___________ sleep as synapses weaken. Experiments show a reduction in the size of dendritic spines during sleep.
slow wave sleep
What is the Glymphatic Drainage hypothesis? What evidence was discussed in favour of/against this hypothesis?
- Glymphatic Drainage Hypothesis: Proposes that sleep allows the brain to “wash away” metabolic waste products, including toxins like beta-amyloid, through a specialised system involving cerebrospinal fluid (CSF).
- This system, discovered by Nedergaard’s lab, increases efficiency during sleep, particularly during SWS. Astrocytes facilitate the process by shrinking to allow more space for fluid flow.
- Evidence: During sleep, greater flow of tracer dyes through paravascular spaces is observed, as well as faster clearance of toxins.
- Criticism: Some studies have shown contradictory results, where waste clearance can also occur during wakefulness in certain conditions.
Quote: “There’s a one-way plumbing system in the brain that washes away metabolic waste, and this is facilitated by sleep.” Source: Lecture 14, Section “Glymphatic Drainage”
What is the Glymphatic Drainage hypothesis?
Glymphatic Drainage Hypothesis proposes that sleep allows the brain to “wash away” metabolic waste products, including toxins like beta-amyloid, through a specialised system involving cerebrospinal fluid (CSF).
________ ______ hypothesis proposes that sleep allows the brain to “wash away” metabolic waste products, including toxins like beta-amyloid, through a specialised system involving cerebrospinal fluid (CSF).
Glymphatic Drainage hypothesis proposes that sleep allows the brain to “wash away” metabolic waste products, including toxins like beta-amyloid, through a specialised system involving cerebrospinal fluid (CSF).
Glymphatic Drainage hypothesis proposes that sleep allows the brain to “wash away” metabolic waste products, including toxins like beta-amyloid, through a specialised system involving ______ ______.
cerebrospinal fluid (CSF).
Glymphatic Drainage hypothesis proposes that sleep allows the brain to “wash away” metabolic waste products, including toxins like beta-amyloid, through a specialised system involving cerebrospinal fluid (CSF).
This system, discovered by __________’s lab, increases efficiency during sleep, particularly during SWS. Astrocytes facilitate the process by shrinking to allow more space for fluid flow.
Glymphatic Drainage hypothesis proposes that sleep allows the brain to “wash away” metabolic waste products, including toxins like beta-amyloid, through a specialised system involving cerebrospinal fluid (CSF).
This system, discovered by Nedergaard’s lab, increases efficiency during sleep, particularly during SWS. Astrocytes facilitate the process by shrinking to allow more space for fluid flow.
