Task 6 body and behavior sleep
What is the function of sleep?
What Is Sleep?
Sleep is a behavior
- What characterizes sleep is that the insistent urge of sleepiness (a
motivation) forces
us to seek out a quiet, warm, comfortable place; lie down; and remain
there for several hours (a behavior).
- Because we remember very little about what happens while we sleep, we
tend to think of sleep more as a change in consciousness than as a
behavior.
Sleep is an altered state of consciousness with distinct behaviors (reduced
movement, stereotypical posture) and specific EEG patterns. Human sleep
cycles through several stages multiple times per night.
- Although we do not respond very much to the environment while we are
asleep, we are not unconsciousness
Sleep is a special biological state with:
reduced responsiveness to external stimuli
stereotyped posture
reduced movement
distinctive electrical brain activity patterns
Function
It is essential for memory, restoration, brain development, and
coordination of biological rhythms.
- Energy Conservation
Reduced metabolism during sleep: lower heart rate, blood pressure,
body temperature, respiration, and muscle tension
Small mammals sleep more to conserve energy due to high
metabolic rates
- Niche Adaptation
Sleep enforces diurnal (active during the day)/nocturnal (active
during the night) patterns appropriate to ecological niche
Sleep enforces this pattern because it forces inactivity at times when
being awake would be risky or inefficient
- Restoration
Sleep restores the body and brain (homeostasis):
o Repairs tissues, supports immune function
o Clears waste products (e.g., β-amyloid) from the brain
The Free Radical Flux Theory of Sleep: proposes that
sleep's primary job is to act as the brain's antioxidant
system, clearing out harmful free radicals (reactive
, oxygen species or ROS) that build up during active
wakefulness
o Links to reduced disease risk (diabetes, cancer, cognitive
decline)
- Memory Consolidation
NREM sleep: consolidates declarative memory (facts, events)
REM sleep: consolidates nondeclarative memory (skills, pattern
learning)
Sleep spindles (Stage 2) → strengthen newly learned information.
Sleep “replays” neuronal activity from learning sessions to
strengthen synapses
Sensory cues during NREM (odor, sound) can enhance memory
consolidation
Sleep deprivation impairs memory, increases false memories
* Source: Breedlove
Functions of Slow-Wave Sleep
Synaptic downscaling: reduces unnecessary synaptic strength built
up during the day.
Highest adenosine levels lead to pressure for SWS; sleep clears
adenosine.
Important for recovery from daily brain activity.
Supports explicit/declaritive memory consolidation.
Functions of REM Sleep
Brain development (infants spend ~70% of sleep in REM).
Emotional processing and creativity.
Strengthens implicit learning (procedures, patterns).
Prepares brain circuits for waking performance.
* Source: Carlson
What brain areas are involved in sleep?
SCN, pineal gland, reticular formation (flip-flop)
Brain Activity During Sleep
- Consciousness During Sleep:
Although we appear unresponsive, the brain is active, and people
can be aware of stimuli.
Sleep is not total unconsciousness; waking people during sleep
reveals conscious experiences.
- REM Sleep:
Cerebral blood flow:
o High in extrastriate cortex (visual association) visual
hallucinations
o low in striate cortex (primary visual) and prefrontal cortex
poor planning, disorganized dreams.
, Lucid dreaming: May involve activation of prefrontal cortex; tDCS
studies suggest dorsolateral prefrontal cortex can increase lucid
dreams.
Eye movements: Correspond to dream imagery; cortical and
subcortical motor regions activate as if performing dream actions
(movement, talking, listening).
- Slow-Wave Sleep:
Overall brain activity and blood flow decrease.
Localized increases in visual and auditory cortex may support
dreamlike imagery.
Decreased blood flow in thalamus and cerebellum.
* Source: Carlson
What are the different stages of sleep?
Sleep stages
Measuring sleep and stages
Sleep is identified using:
EEG (brain waves/activity)
EOG (eye movement)
EMG (muscle tone)
What is the function of sleep?
What Is Sleep?
Sleep is a behavior
- What characterizes sleep is that the insistent urge of sleepiness (a
motivation) forces
us to seek out a quiet, warm, comfortable place; lie down; and remain
there for several hours (a behavior).
- Because we remember very little about what happens while we sleep, we
tend to think of sleep more as a change in consciousness than as a
behavior.
Sleep is an altered state of consciousness with distinct behaviors (reduced
movement, stereotypical posture) and specific EEG patterns. Human sleep
cycles through several stages multiple times per night.
- Although we do not respond very much to the environment while we are
asleep, we are not unconsciousness
Sleep is a special biological state with:
reduced responsiveness to external stimuli
stereotyped posture
reduced movement
distinctive electrical brain activity patterns
Function
It is essential for memory, restoration, brain development, and
coordination of biological rhythms.
- Energy Conservation
Reduced metabolism during sleep: lower heart rate, blood pressure,
body temperature, respiration, and muscle tension
Small mammals sleep more to conserve energy due to high
metabolic rates
- Niche Adaptation
Sleep enforces diurnal (active during the day)/nocturnal (active
during the night) patterns appropriate to ecological niche
Sleep enforces this pattern because it forces inactivity at times when
being awake would be risky or inefficient
- Restoration
Sleep restores the body and brain (homeostasis):
o Repairs tissues, supports immune function
o Clears waste products (e.g., β-amyloid) from the brain
The Free Radical Flux Theory of Sleep: proposes that
sleep's primary job is to act as the brain's antioxidant
system, clearing out harmful free radicals (reactive
, oxygen species or ROS) that build up during active
wakefulness
o Links to reduced disease risk (diabetes, cancer, cognitive
decline)
- Memory Consolidation
NREM sleep: consolidates declarative memory (facts, events)
REM sleep: consolidates nondeclarative memory (skills, pattern
learning)
Sleep spindles (Stage 2) → strengthen newly learned information.
Sleep “replays” neuronal activity from learning sessions to
strengthen synapses
Sensory cues during NREM (odor, sound) can enhance memory
consolidation
Sleep deprivation impairs memory, increases false memories
* Source: Breedlove
Functions of Slow-Wave Sleep
Synaptic downscaling: reduces unnecessary synaptic strength built
up during the day.
Highest adenosine levels lead to pressure for SWS; sleep clears
adenosine.
Important for recovery from daily brain activity.
Supports explicit/declaritive memory consolidation.
Functions of REM Sleep
Brain development (infants spend ~70% of sleep in REM).
Emotional processing and creativity.
Strengthens implicit learning (procedures, patterns).
Prepares brain circuits for waking performance.
* Source: Carlson
What brain areas are involved in sleep?
SCN, pineal gland, reticular formation (flip-flop)
Brain Activity During Sleep
- Consciousness During Sleep:
Although we appear unresponsive, the brain is active, and people
can be aware of stimuli.
Sleep is not total unconsciousness; waking people during sleep
reveals conscious experiences.
- REM Sleep:
Cerebral blood flow:
o High in extrastriate cortex (visual association) visual
hallucinations
o low in striate cortex (primary visual) and prefrontal cortex
poor planning, disorganized dreams.
, Lucid dreaming: May involve activation of prefrontal cortex; tDCS
studies suggest dorsolateral prefrontal cortex can increase lucid
dreams.
Eye movements: Correspond to dream imagery; cortical and
subcortical motor regions activate as if performing dream actions
(movement, talking, listening).
- Slow-Wave Sleep:
Overall brain activity and blood flow decrease.
Localized increases in visual and auditory cortex may support
dreamlike imagery.
Decreased blood flow in thalamus and cerebellum.
* Source: Carlson
What are the different stages of sleep?
Sleep stages
Measuring sleep and stages
Sleep is identified using:
EEG (brain waves/activity)
EOG (eye movement)
EMG (muscle tone)
