Transcript Sleep, Rhythms & Timing

Biological Rhythms & Sleep
• Is there a biological clock?
• Is there a role for environmental cues?
• Neural substrates of the clock
– SCN
– Pineal gland
• Sleep
Environment
Circa annual
Circa dian
Ultradian
Behavior
• Season
• Migration / Hibernation
• Month
• Menstrual cycle
• 24 hs cycle
(light/dark)
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Wake / sleep
Hormone release
Body temperature
Intra ocular pressure
sensitivity to drugs
Question: Does the environment drive the behavioral cycles?
How can we test this hypothesis?
• Assess the behavioral cycle when
– the environmental cue is absent (constant darkness)
– the environmental cue is shifted (jet lag)
– the environmental cue is not processed (retinal blindness)
Does the environment drive the behavioral cycles?
Environmental cues
Dark
Behavior
Activity
Light
X
Dark room situation
Rest
Internal
Clock
Dark
Activity
Light
Rest
X
Dark room situation
Internal Clock
(but with 25 hs cycle)
1. the cycle is driven by an internal clock
2. but environmental cues do entrain the clock
1. the cycle is driven by an
internal clock
2. environmental cues
do entrain the clock
Where in the brain is this Circadian
Biological Clock?
Light-dark cycle
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Constant dim light
Lesion to the
Suprachiasmatic
nucleus (SCN)
Gene mutation for
Clock protein in SCN cells
-Environmental cues reset
the biological clock
Bright Light can reduce
Jet lag
later
sunset
- Lowest point in body
temperature is usually
before wake-up
1-2 hs
Bright Light earlier than that
point delays the cycle (‘later
sunset’)
Bright Light later than that
point advances the cycle
(‘earlier sunrise’)
earlier
sunrise
SCN Biological Clock
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SCN cells have a circadian rhythm
SCN lesions disrupt circadian rhythms
SCN receives input from retina (light resets clock)
SCN transplant: rhythm is controlled by donor’s cells
 The SCN clock has a genetic component
(Clock/Per
genes)
 Individual differences in sleep patterns may be
related to these genetic differences (are you a ‘nigh owl’?)
 The circadian rhythm also depends on the pineal gland
The SCN clock has a genetic component
The molecular changes
oscillate with a 25 hs period
- Light modulates the period
Pineal gland: Another part of the clock
• The pineal gland
secretes melatonin
• Melatonin acts on SCN
• SCN acts on pineal
gland, via the cervical
ganglion of the
sympathetic system
• Both SCN and pineal
gland have circadian
patterns
• Melatonin release peaks soon after dark
• Melatonin is effective in reducing jet lag, BUT
• Its effectiveness depends on time of day because
• receptors for melatonin have circadian rhythm
Sleep
• Sleep Stages
– Behavioral profiles
– Neural Systems
– Developmental changes
• Sleep deprivation
• Sleep Functions
• Sleep pathology
Stages of Sleep
 Non-REM
 Stages 1 and 2 (light)
 Stages 3 and 4:
 slow-wave
(synchronized)
 difficult to raise from it
 Muscle control (toss
and turn)
 REM
 Desynchronized
 PGO waves
 Vivid dreams
 sexual arousal
 no muscle tone
(paralysis)
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REM: 1. Famous rock band; 2. Rapid-eye movements
• Behavior:
– Muscular Paralysis
– Penile Erection (not necessarily related to sexual dream)
• Cognition & Perception
– Dreams (w/ story line & perceptually rich)
• Neuronal Activity
– Desynchronize (EEG)
– PGO waves
– Cortical activation
• Neurotransmitters:
– High Ach
– Low NE (see Graph next slide)
– Low 5HT
Dreams
REM
Cerebral Cortex
Lateral
Geniculate
Nucleus
Superior
colliculus
Ach neurons
PONS
Paralysis
Motoneurons
Nucleus
In Brainstem
(-)
Locus
Coeruleus
(Noradrenaline)
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Developmental
Changes in Sleep
Developmental Changes in Sleep
• Rhythm of Awake/Sleep Cycle: absent in newborns
• Overall Duration of Sleep:
– High in newborns,
– Reduced in the elderly
• Phases of Sleep
– Infants: Lots of REM, stage 4
– Elderly: reduced REM
• Wake-up time
– Infants (< 2 years): Early (6-8 am), independent from bedtime!!
– Adolescent: late morning
– Elderly: Early morning
• Individual differences exist
young
-Elderly:
Shorter cycles
Reduced REM
Reduced Stage 4
Sleep deprivation
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Increases irritability
reduces cognitive performance
May depress the immune system
Extreme deprivation may produce death
– genetic mutation and/or thalamic lesion
– Rats under sleep deprivation (stress??)
• Reduced body temperature
• Immune suppression
• Increased metabolism
What is the Function of Sleep?
 Nobody knows!
 Sleep as an adaptive response?
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Found in all vertebrates (REM in mammals)
Kept our ancestors our of predators way?
Conserves energy (may be in small animals)
 Restoration and repair?
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Reduced brain activity during Slow Wave Sleep (Sws)
Changes in sleep during:
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Prolonged bed rest (no real changes in SWS)
Exercise (temperature increas. => increase SWS)
Mental activity increases SWS (?)
9.12
What is the Function of Sleep?
• Memory consolidation
– Loss of sleep -> memory deficits
– Increased sleep after learning (?)
– Spatial learning in rats -> REM & place code
cells
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Sleep Disorders
 Sleep deprivation (social vs. biological factors)
 Toddlers: 9 pm bedtime vs. 6 am wake up
 Parents of infants: 11 pm bedtime vs. 6 am wake up
 Young adults: 8 am class vs. delayed wake up
 Insomnia: Difficulty in sleeping
 Many causes: situational, drug-induced
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Sleeping pills: drug-dependence insomnia
Sleep Disorders (cont’d)
 Narcolepsy: urge to sleep
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Triggered by boring events
Genetic component (mice, dogs)
Atrophy of hypocretin neurons in hypothalamus
Quick transition from awake to REM
 Cataplexy: awake paralysis
 Triggered by exciting events
 Co-occurs with narcolepsy
 In normal subjects --> sleep paralysis
Sleep Disorders (cont’d)
 REM without atonia:
 ‘act out’ the dreams
 Disorder of slow wave sleep
 Sleep walking
 Night Terrors
Rhythms
• Is there a biological clock?
• Is there a role for environmental cues?
• Neural substrates of the clock
– SCN
– Pineal gland
Sleep deprivation
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Increases irritability
reduces cognitive performance
May depress the immune system
Extreme deprivation may produce death
– genetic mutation and/or thalamic lesion
– Rats under sleep deprivation (stress??)
• Reduced body temperature
• Immune suppression
• Increased metabolism
• Activities
– sleep diary (ask george)
– morning/evening questionnaire
–