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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 Season Month 24 hs cycle (light/dark). Behavior Migration / Hibernation Menstrual cycle Wake / sleep - PowerPoint PPT Presentation
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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
• Season
• Month
• 24 hs cycle (light/dark)
Behavior• Migration / Hibernation
• Menstrual cycle
• Wake / sleep• Hormone release• Body temperature• Intra ocular pressure• sensitivity to drugs
Circa annual
Circa dian
Ultradian
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)
Environmental cues Behavior
Does the environment drive the behavioral cycles?
Internal ClockX
Dark room situation
Dark
Light Rest
Activity
Internal Clock(but with 25 hs cycle)
Dark room situation
X
Dark
Light Rest
Activity
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
Lesion to theSuprachiasmatic nucleus (SCN)
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
Constant dim light
Gene mutation for Clock protein in SCN cells
-Environmental cues reset the biological clock
Bright Light can reduceJet lag
- Lowest point in body temperature is usually 1-2 hs before wake-up
Bright Light earlier than that point delays the cycle (‘later sunset’)
Bright Light later than that point advances the cycle (‘earlier sunrise’)
earlier sunrise
later sunset
SCN Biological Clock
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
- Light modulates the period
The molecular changes oscillate with a 25 hs 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
Retina
LGN (thalamus)
primary visual cortex
Superior colliculus
Suprachiasmatic n. (hypothalamus)
other hypothalamic nuclei
pineal gland
melatonin
vision
other visual areas
eye movements
circadian rythms
SNA
drinking sleep hormones secretion
eating
stroke (blind with normal circadian rythm)
Sleep
• Sleep Stages – Behavioral profiles– Neural Systems– Developmental changes
• Sleep deprivation
• Sleep Functions
• Sleep pathology
Stages of Sleep
REM Desynchronized PGO waves
Vivid dreams sexual arousal no muscle tone
(paralysis)
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: 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
Ach neuronsPONS
Superiorcolliculus
REM
LocusCoeruleus
(Noradrenaline)
LateralGeniculate
Nucleus
Cerebral Cortex
Nucleus In Brainstem
Dreams
(-)
Motoneurons
Paralysis
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
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
Developmental Changes in Sleep
young
-Elderly: Shorter cycles Reduced REM
Reduced Stage 4
Sleep deprivation
• 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?
Found in all vertebrates (REM in mammals) Kept our ancestors our of predators way? Conserves energy (may be in small animals)
Restoration and repair? Reduced brain activity during Slow Wave Sleep (Sws) Changes in sleep during:
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
•
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
Sleeping pills: drug-dependence insomnia
Sleep Disorders (cont’d)
Narcolepsy: urge to sleep 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
• 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–
