Sleep and Biological Rhythms

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Sleep and Biological Rhythms
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Lecture Outline

• Stages of sleep
• Sleep function
• Neural control of sleep
• Sleep Disorders
• Rhythms

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EEG Studies of Sleep

• Sleep/waking cycle is experienced each day
• Physiological changes that occur during sleep
• Muscle tone (EMG)
• Brain wave activity
• Synchrony vs desynchrony
• Eye movements
• Genital activity

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Alpha 8-12 Hz Beta 13-30 Hz Theta 3.7-7.5
Hz Delta lt 3.5 Hz
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Non-REM Sleep

• Alpha, delta, theta activity in the EEG
• Stages 1 and 2 theta
• Stages 3 and 4 delta activity (synchronized)
• Termed slow-wave sleep (SWS)
• Light, even respiration
• Muscle control is present (toss and turn)
• Dreaming
• Difficult to rouse from stage 4 SWS (resting
  brain?)

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REM sleep

• Presence of beta activity (desynchronized)
• Enhanced respiration and blood pressure
• Rapid eye movements (REM)
• PGO waves
• Loss of muscle tone (paralysis)
• Vivid, emotional dreams
• Signs of sexual arousal
• Assess impotence stamps versus the sleep lab

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Cycling of SWS and REM
1. SWS precedes REM sleep 2. REM sleep
lengthens over the night 3. Basic sleep cycle
90 minutes
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What is the Function of Sleep?

• Sleep as an adaptive response?
• Found in all vertebrates (REM in mammals)
• Kept our ancestors our of predators way?
• Restoration and repair?
• Reduced brain activity during SWS
• Changes in sleep duringProlonged bed rest (no
  real changes in SWS)
• Exercise (temperature inc. gt inc. SWS)
• Mental activity increases SWS

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Sleep Deprivation Studies

• Human Sleep Deprivation
• Peter Tripp 200 hrs sleep deprivation produces
  psychosis
• Randy Gardner sleep deprivation does not induce
  psychosis
• Perhaps drugs taken by Tripp contributed to
  psychosis
• Sleep deprivation impairs cognitive functions
• Perceptual distortions and hallucinations
• Animal Sleep Deprivation Studies
• Rats forced to walk lose sleep
• Eat more, increased activity, illness and then
  death

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Sleep Functions

• SWS may reflect restoration
• REM sleep may reflect
• Vigilance alertness to the environment
• Consolidation of learning/memory
• Flushing of useless information
• Facilitation of brain development

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Chemical Modulation of Sleep/waking?

• Notion of sleep-promoting or wakefulness-promoting
  factors?
• Unlikely given
• Siamese twins share circulatory system but sleep
  independently
• Bottle-nose dolphins two hemispheres sleep
  independently
• But adenosine receptor stimulation increases slow
  wave sleep

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Sleep in Bottle-Nose Dolphins
Figure adapted from Mukhametov, L.M. in Sleep
Mechanisms, edited by A.A. Borbely and J.L.
Valatx. Munich Springer-Verlag, 1984.
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Neural Regulation of Arousal

• Electrical stimulation of brainstem induces
  arousal
• Dorsal path RF--gt to medial thalamus --gt cortex
• Ventral path RF --gt to LH, basal ganglia,
  forebrain
• Neurotransmitters involved in arousal
• NE high activity when wake, low during sleep
  (LC)
• ACh agonists increase arousal, antagonists
  decrease arousal
• 5-HT raphe nuclei activity is low during sleep
• 5-HT neurons were most active during wakefulness,
  activity declined during SWS, and reached 0
  during REM sleep

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Locus Coeruleus and Arousal

• NE secretion inhibits sleep (amphetamine)
• Lesions of ascending LC fibers increase REM,
  slow wave sleep
• Correlation of LC NE neurons with sleep-waking
  cycle
• LC firing rate declines during REM sleep
• LC firing rates increases on awakening

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• Physiological Mechanisms of Sleep and Waking
• Neural control of slow-wave sleep
• Ventrolateral preoptic area (VLPA)
• A group of GABAergic neurons in the preoptic area
  whose activity suppresses alertness and
  behavioral arousal and promotes sleep.
• Destruction of this area has been reported to
  result
• in total insomnia, coma, and eventual death in
  rats.

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Dorsolateral Pons and REM Sleep

• Pontine neurons initiate REM sleep
• PGO waves are first predictor of REM sleep
• ACh levels elicit PGO waves
• Increased ACh increases REM sleep
• Decreased ACh decreases REM sleep (kainic acid
  lesions)
• Pontine lesions decrease REM sleep (Israeli
  soldier)
• Pontine cells project via magnocellular cells
  within medulla to the spinal cord release
  glycine to inhibit alpha-motoneurons (induce
  paralysis or atonia)

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Sleep Disorders

• Insomnia Difficulty in sleeping
• Many causes situational, drug-induced
• Sleeping pills drug-dependence insomnia
• apnea
• Narcolepsy Sleep at odd times
• Sleep attack urge to sleep
• Cataplexy REM paralysis
• Sleep paralysis
• Hypnagogic Hallucinations

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Sleep Disorders

• Parasomnias
• Night terrors
• Enuresis
• Sleep-talking
• Sleep-walking
• REM w/o atonia
• Myoclonic jerk reflex
• PLMD- Periodic limb movement disorder

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Biological Rhythms

• Behaviors display rhythmic variation
• 90 minute rest-activity cycle
• Circadian about a day
• e.g. sleep/waking cycle, temperature
• Monthly rhythms
• Menstrual cycle
• Seasonal rhythms
• e.g. aggression, sexual activity in deer

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SCN and Circadian Rhythms

• Suprachiasmatic Nucleus (SCN) contains a
  biological clock that governs circadian rhythms
• SCN receives input from retina (light resets
  clock)
• SCN lesions disrupt circadian rhythms
• SCN clock cells do not require direct neural
  connections to control circadian rhythms

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SCN Biological Clock

• SCN cells exhibit circadian rhythms
• Involves glucose metabolism
• Appears to be synchronized by SCN chemicals
• Nature of clock
• Fruit fly analogy
• Activity of PER and TIM genes
• Light pulses inhibit TIM gene
• Resets circadian cycle