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lambert_chapter_9PPT.pptxChapter 9
Sleep, Wakefulness, and Conscious Awareness
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Outline
The Rhythms of Sleep and Wakefulness
The Neurobiology of Sleep
Why Sleep and Dream?
Sleep Patterns: Typical and Atypical Variations
Altered States of Consciousness: Beyond Sleep
Rhythms of sleep/wake
Circadian Rhythms
Stages of Sleep
Extreme Sleep: Hibernation
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Rhythms of sleep/wake
Circadian vs. ultradian
Why can’t we just rely on external environment for temporal cues?
How often do we mess up our sleep schedule?
Rhythms of sleep/wake
Why do so many species yawn?
Yawning across species. Scientists continue to debate the evolutionary advantage of yawning and why it occurs in many species, including (a) apes, (b) lions, (c) dogs, and (d) humans.
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Rhythms of sleep/wake: Melatonin
Figure 9.2
Neural circuits involved in circadian rhythms and peak melatonin response. Melatonin appears to be a chemical trigger signaling increased blood flow in distal areas of the body, promoting heat loss and the onset of sleep.
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Rhythms of sleep/wake: Sleep
Sleep occurs in stages
Characteristic EEG signals during each stage
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Rhythms of sleep/wake: Sleep
Stages of sleep. Over the course of a night, sleeping individuals cycle through several distinct stages: Stages 1 and 2, slow wave sleep, and REM sleep, during which dreams occur. A polysomnograph records the different brain wave patterns that characterize these stages.
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Rhythms of sleep/wake: Sleep
A full night’s rest. Slow wave sleep decreases and REM sleep increases as the night progresses.
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Rhythms of sleep/wake: Hibernation
Why would an animal hibernate?
Are there any obvious downsides to sleeping through the winter?
Hibernation. Many animals, such as the (a) chipmunk, enter an extended state of unconsciousness (b) in response to harsh winter weather.
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Neurobiology of sleep
Early Neuroanatomical Explorations
Sleep as lack of sensory input?
Tests via lesion method on nonhumans
Neuroanatomical / Neurochemical Circuits
Acetylcholine
SWS: GABA, galanin, adenosine
REM: PGO spikes
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Neurobiology of sleep: ARAS
The ascending reticular activating system (ARAS). The ARAS conveys sensory information to other parts of the brain and is essential for maintaining wakefulness.
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Neurobiology of sleep: Acetylcholine
The neurochemistry of wakefulness. tegmental nuclei (LDT) contributes to the maintenance of wakefulness. Acetylcholine from the pedunculopontine tegmental nuclei (PPT) and laterodorsal
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Neurobiology of sleep
Total sleep could be dangerous for some animals
Why not just never sleep?
Dolphin sleep. EEG records of dolphins reveal that only one hemisphere sleeps at a time.
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Neurobiology of sleep: SWS
Hypothalamic projections from the ventrolateral preoptic area (VLPO) to the tuberomammillary nucleus (TMN) function to diminish wakefulness during slow wave sleep.
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Neurobiology of sleep
Which animal is experiencing REM sleep?
Why is loss of muscle tone advantageous during REM sleep?
Cat naps. The sleeping posture of animals reveals information about the stage of sleep they are currently in. (a) The ability of the cat to hold its head up indicates that it is in non-REM sleep. (b) This cat has apparently lost muscle tone and entered REM sleep.
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Neurobiology of sleep: REM
Why dream?
Activation-synthesis model
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Neurobiology of sleep: REM
Pontine nuclei and REM characteristics. Lesions of pontine nuclei diminish specific aspects of REM sleep.
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Why sleep and dream?
Homeostatic theory of sleep regulation
Adaptive theory of sleep
Cultural differences in sleep patterns
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Why Sleep?
How would you test the role of sleep?
What ethical concerns should we be aware of?
Why Sleep?
Rats kept awake long enough got sick, stopped eating, died
Rodent model of sleep deprivation. Electroencephalograms recorded from the experimental animals activate the movement of the platform when the animal sleeps so that the disk movement and threat of falling in the water wake the animal up. The yoked animal also has its sleep patterns disrupted by the platform movement, but, unlike the experimental animal, it can engage in occasional sleep.
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Why Sleep? Adaptive theory
Sleep patterns should reflect environmental demands
Different animals show very different sleep patterns
Environment change (e.g., captivity) can change sleep habits
Maybe we’ve been too hard on sloths
Why Sleep?
Variation exists in human sleep schedules
Number of sleep periods
Not all members of community sleep at same time
Not everyone sleeps same duration
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Why Sleep?
Sleep may also play a role in learning and memory
Memory consolidation
Sleep replay
Synaptic homeostasis hypothesis
Theta rhythms and offline processing
Why Sleep? Sleep Replay
Sleep and learning. (a) When a rat sleeps after navigating through a maze, the same neural patterns that the rat displayed while in the maze are reactivated. (b) In humans, presentation of stimuli during a learning task and subsequently when a subject is in slow wave sleep can reactivate neural patterns similar to those active during learning, facilitating consolidation of the information.
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Why Sleep? Theta rhythms
θ rhythms during REM and waking behaviors. Similar θ rhythms observed during both REM and survival-related behaviors in various mammals suggest that REM brain activity may facilitate these behaviors expressed during waking hours.
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Why Sleep? Immune function
Vaccine effectiveness in the sleep deprived?
Sleep efficiency vs. sleep amount
Neurons responsive to immune chemicals are located in sleep/wake regions
brainstem, hippocampus, hypothalamus
Immune chemicals increase during SWS
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Sleep Patterns: Typical vs. Atypical
How do we define what “normal” sleep is?
Take the average, take the mode?
What if most people are not getting “enough” sleep?
Sleep durations in the United Kingdom and the United States. Sleep durations are evenly distributed in (a) the United Kingdom and (b) the United States, with an average nightly sleep of approximately seven hours in both groups.
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Sleep Disorders
Insomnia
GABA implicated
Narcolepsy
Hypocretin/orexin system implicated
Sleep apnea
Obstructed airways, associated with obesity
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Sleep disorders: Insomnia
No single treatment for Insomnia
Cognitive-Behavioral Therapy for Insomnia
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Sleep disorders: Narcolepsy
The hypocretin system. Hypocretin/orexin cells are located in the hypothalamus. They project to areas throughout the brain, influencing wakefulness and other functions related to energy expenditure and emotional processes.
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Sleep disorders: Sleep apnea
Sleep apnea and brain volume. Postmortem analyses of individuals with obstructive sleep apnea revealed smaller cortical areas (shown in red) compared with healthy control brains.
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Altered states of consciousness
Neural networks and conscious awareness
Disorders of consciousness
Hard to study consciousness, hard to define disorders
Death and the end of consciousness
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Conscious Awareness Network
Dissociation in brain regions for internal/external attention
Internal and external awareness. Specific brain areas are activated during internal and external conscious awareness. These functional magnetic resonance imaging scans show more activation in the cingulate cortex and parahippocampal cortex (blue) in strong internal awareness and more activation in the dorsolateral prefrontal cortex and inferior parietal lobe (red) during strong external awareness.
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Disordered Consciousness
Conditions to keep straight
Locked-in syndrome
Vegetative state
Minimally conscious
Coma
Brain death
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Disordered Consciousness
Minimally conscious patients show brain activity in response to questions
Minimal behavioral response
Brain responsiveness of minimally conscious patient. When asked to imagine hitting a ball on a tennis court (A/B) and navigating through a city or their home (C/D), a minimally conscious patient and a healthy individual showed similar brain response patterns.
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Brain death vs. vegetative state
Brain death. There is virtually no observable resting brain activity in positron emission tomography scans of individuals diagnosed with brainstem, or brain, death.
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