Rhythms of The Brain

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Rhythms of The Brain
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Biological Rhythms

• Circannual - year
• Circadian - daily
• Biological Clocks time our rhythms

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Human Circadian Rhythm
6 months in a cave!
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Actual vs. Endogenous Rhythm
endogenous
Without natural cues, sleep-wake cycles around a
25 hr day Environmental cues (zeitgebers) resynch
ronize internal clock to a 24-hr day.
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What IS The Clock?
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Suprachiasmatic Nucleus (SCN) of the hypothalamus

• Retinohypothalamic - path from retina to SCN
• Lesion - behaviors continue but at inappropriate
  times
• Intrinsic rhythmicity
• Cut input/outputs
• Individual neurons show rhythm in a dish
• Induce rhythm when transplanted (lesioned, normal)

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SCN CONTROLS PINEAL GLAND WHICH PRODUCES
MELATONINMELATONIN can make you sleepybut
sleep is not dependent on it
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Sleep Physiology

• EEG Electroencephalography

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EEG Patterns During Different States
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Sleep Stages(EEG)
REM Rapid Eye Movement Paradoxical Sleep
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Cycling Sleep Stages
Multiple Cycles each night REM lengthens
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NREM Sleep

• Walking, talking screaming in your sleep
• Night terrors
• Age 5-7 years
• Feeling of uncontrollable panic, accompanied by
  increased heart rate, blood pressure

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REM Dreaming

• Eyes move, toes, fingers, mouths twitch
• Everyone dreams.why?
• Activation-synthesis hypothesis
• Random activation of cortex by brainstem. Cortex
  generates images, actions emotions from memory
  stores
• Evolutionary hypothesis
• Lead to enhanced performance in dealing w/
  threatening life events

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Do We Need Sleep?

• Spend 1/3 of life
• Highly conserved

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Total deprivation in some animals death
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Human Deprivation

• A debt is created
• Psychosis
• Irritability
• Difficulty concentrating
• Disorientation
• Memory impairment

Randy Gardner (1963), 17 yrs old, 11 days w/out
sleep Irritable, nausea, memory problems, mild
delusions, tremors Speech slurred, no EEG alpha
waves. When he slept 15 hrs Butno lasting
harmful effects
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Response to Sleep Deprivation
Fall asleep quickly

• Sleep Rebound
• Increased intensity, duration
• REM and slow wave sleep

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Why Do We Need Sleep?

• Biological Adaptation
• Energy conservation predator/prey keeps us
  quiet when we cant move around well
• Restoration
• NREM - free radical repair
• REM - reset monamine sensitivity
• Memory
• Rats and humans replay events in their sleep

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Neural Basis of Sleep

• Reticular Formation
• maintains cortical arousal waking EEG
• turns NREM on and off

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• Sensory input activates RAS which desynchronizes
  cortical EEG
• Destroy RAS - coma, Karen Ann Quinlan

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Neural Basis of REM

• Damage - disrupts REM
• Projections to cortex motor areas of medulla
  events related to REM
• muscle paralysis
• Waking EEG

Initiates REM
Produces REM activities
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Lesions to descending makes a Sleep -Walking Cat
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Sleep Disorders

• Sleep apnea
• Narcolepsy

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Sleep Apnea

• Apnea want of breath
• Central (brainstem)
• Obstructive
• Chronically tired, often not aware of the
  episodes, high blood pressure
• Treatment - many surgery to life style changes

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Snoring
Apnea
Nasal Continuous Positive Airway Pressure (CPAP)
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Narcolepsy

• Main Symptoms
• Excessive daytime sleepiness
• Cataplexy - sudden loss of voluntary muscle
  control (usually triggered by emotions) person is
  alert
• Sleep paralysis during transition from sleep to
  waking
• Hypnogogic hallucinations - REM sleep while
  conscious

It is an abnormal intrusion of the
characteristics of REM sleep into waking.
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What Causes it?

• Degeneration or absence of hypothalamus cells
  producing hypocretin (aka orexin) peptide
  essential to the human sleep-wake cycle
  (autoimmune?).
• Hypocretin knockout mice narcoleptic
• Result- disruption of RAF nuclei which control
  various aspects of sleep
• TREATMENT
• frequent naps, stimulants (Ritalin), tricyclic
  antidepressants (suppress REM)