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Week 29 > EEG and Sleep > Flashcards

EEG and Sleep Flashcards

1
Q

What is EEG?

A

Electroencephalogram

  • recording of the rhythmic activity of the brain
  • made from the cerebral cortex
  • electrodes placed on the skull
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2
Q

Richard Caton

A
  • first person to probe the brain of animals with electrodes
  • Discovered electrical brain signals
  • used a reflecting galvanometer
    • measure micro-amperes
    • primitive form of amplification
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3
Q

Hans Berger

A
  • First to record EEG from humans
  • defined all major EEG rhythms
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4
Q

Basic EEG Frequencies:

A
  • Alpha Rhythm
    • 8-13 Hz
    • awake, relaxed adults
    • closed eyes
  • Beta Rhythm
    • 13-30 Hz
      • higher frequencies
    • awake adults
    • open eyes
  • Theta Rhythm
    • 4-7 Hz
      • slower higher amplitude
    • drowsiness
  • Delta Rhythm
    • 0.5-4Hz
      • very slow, high amplitude
    • Sleep
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5
Q

Mechanism of EEG

A
  • All the action potentials on the neuronal cell bodies
  • EEGs are derived from alternating excitatory or inhibitory synaptic potentials
  • in cortical neurons as a result of thalamocortical inputs (and other inputs)
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6
Q

What is the principle source of EEG electrical activity?

A
  • Pyramidal cells
    • projects from the thalamus to the contralateral cortex
    • sum of all excitatory or inhibitory synaptic potentials
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7
Q

EEG as a diagnostic tool:

A
  • Coma-EEG
    • Mainly Delta Activity
  • Brain Dead:
    • sustained flat EEG reading
  • Epilepsy: (petit mal)
  • Epilepsy (grand mal)
  • Partial Seizures
    • spikes in affected areas
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8
Q

EEG: Test the integrity of sensory pathway

A
  • SEP
    • somatosensory evoked potentials
    • cortical potentials generated by the response of sensory neurons to the stimluation of peripheral nerves
    • ex: stimulate skin on hand
    • If no conductance= peripheral nerve has been severed/damaged
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9
Q

Types of EEG: Comatose patient

A
  • centralized slow waves
  • mainly delta activity
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10
Q

Type of EEG: Epilepsy different types

A
  • Generalized seizures:
    • Grand Mal:
    • Petit Mal
  • Partial Seizures (aka focal seizures)
    • Temporal lobe seizure
    • Focal seizure
    • Secondary Generalized Seizures
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11
Q

Seizure: Definition

A
  • Latin-to take possesion of
  • the clinical manifestation of abnormal, excessive, hypersynchronous discharge of a population of cortical neurons
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12
Q

Epilepsy

A
  • Chronic disorder of CNS
  • recurrent unprovoked seizures
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13
Q

Seizure initiation is characterized by:

A

2 concurrent events:

  • high frequency bursts of action potentials
  • hypersynchronization of neuronal population
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14
Q

Pathway for seizure propagation

A
  • Seizures may start in certain regions then spread
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15
Q

Petit Mal attack (seizure)

A
  • EEG
    • Symmetrical
    • highly synchronized activity
  • aka Absence seizure
  • Milder type of activity
  • causes unconsciousness with no convulsions
    • begins and ends abruptly and without warning
    • blank stare
    • No confusion
    • can Resume activity immediatelly
  • After there is no memory of the seizure
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16
Q

Grand Mal attack (seizure)

A
  • AKA Generalized tonic-clonic seizure
  • usually short cry and fall to the ground
  • Tonic phase
    • muscles will stiffen
  • Clonic phase
    • extremities will jerk and twitch
  • Bladder control may be lost
  • Loss of consciousness and regained slowly
  • Wide distribution of seizure activity to both hemispheres
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17
Q

Similarity between Grand Mal and Petit Mal

A
  • Consciousness is slowest
  • no recollection of the seizure
  • Memory is often lost just in recent events just before the seizure along with the seizure
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18
Q

Focal Cortical Seizures

A
  • AKA Simple partial seizures
  • Result from epileptic activity
  • localized in one hemisphere
    • usually cortex or limbic system
  • Consciousness is not impaired
  • May have abnormal muscle contraction
    • ex: abnormal head movement
  • can usually talk and answer questions
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19
Q

Temporal Lobe seizure

A
  • starts in the temporal lobe
  • Involves sensory changes
    • Ex: smelling an unusual odor
  • Most common cause is:
    • mesial temporal sclerosis
    • hippocampal sclerosis
  • Risk factors
    • Aging
    • Stroke
    • Vascular
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20
Q

Mechanism of Seizure initiation

A
  • Poorly understood
  • initially- local changes in permeability for potassium and calcium ions
    • _​_Increase in extracellular K+ brings membrane closer to threshold
  • Accumulation of Ca2+ in presynaptic terminals, leading to enhanced neurotransmitter release (depolarization)
  • So the depolarization-induced activation of the NMDA subtype of the excitatory amino acid receptor (glutamate)
    • opens more Ca2+ channels–>Ca2+ influx
    • Neuronal activation (from further depolarization due to influx)
21
Q

Seizures: Sensory Stimulations

A
  • May be induced by strong sensory experiences
  • Audiogenic seizures
    • high frequency of sound=Sensory
  • Visual Seizures
22
Q

Sleep

A
  • Normal, easily reversible, recurrent, and spontaneous state of decreased and less efficient responsiveness to external stimuli
  • Eyes closed
  • consciousness completely or partial lost
  • In humans and other mammals the brain undergoes a cycle of brain-wave activity that includes intervals of dreaming.
23
Q

Moruzzi and Magoun: late 1940s

A

2 observations:

  • transection of ascending sensory pathway in the brainstem did not interfere with wakefullness
  • Lesion of RF produced stupor with EEG pattern resembled sleep

Conclusion:

  • tonic activity of RF keeps brain awake
24
Q

Moruzzi & Colleague: Late 1950s

A
  • Transection of the brainstem including RF through the pons
    • greatly reduced sleep
  • Rostral portion of RF
    • above pons
    • contains neurons whose activity-wakefullness
    • Activity was inhibited by neurons in the RF below the pons
25
Q

What are the different areas of the brain that can put someon to sleep or awake if stimulated?

A
  • Awake
    • Rostral Reticular formation
      • Ascending reticular activating system
        • Sleep:
    • Thalamic nuclei
      • intralaminar nucleus
    • Caudal RF
    • Hypothalamus
26
Q

ARAS

A

Ascending Reticualr Activating System

  • aka extra thalamic control modulators system
  • set of connected nuclei in the brain of vertebrae
  • Regulate:
    • Wakefulness
    • sleep-wake transitions
  • Part of the RF
  • Projects to various nuclei in the thalamus and other Brian nuclei associated with NTs
  • Awake
    • RF
      • Rostral part=ARAS
      • project to limbic system and cortex
  • sleep
    • RF
      • caudal part
    • Hypothalamus
    • Thalmic nuclei
27
Q

Brain Nuclei that contribute to sleep-wake

A
  • Sleep:
    • Raphe nuclei
      • serotoninergic
      • brainstem
    • Cholinergic nucleus
      • brainstem
  • Wake
    • Locus Coeruleus
      • brainstem
      • noradrenergic
    • Tuberomammillary nucleus of hypothalamus
      • Hypothalamus
28
Q

Hypothalamic Nuclei: involved in regulation of sleep-wake cycle

A
  • Suprachiasmatic Nucleus
    • control circadian rhythm
    • central pacemaker of circadian timing
      • receives direct input from the retina
      • sends oscillations to other areas of the brain ==>“Slave oscillators) in pineal gland
    • bilateral structure
    • anterior part of hypothalamus
  • Tuberomammillary nucleus
    • histminergic nucleus
    • located in posterior third of hypothalamus
    • consists largely of histaminergic neurons
    • involved in:
      • arousal
      • learning
      • memory
      • sleep
      • energy balance
  • VLPO (Ventrolateral preoptic nucleus)
    • Active during non-REM sleep
    • released inhibitory NTs
      • GABA
      • galanin
29
Q

Regulation of Sleep-wake Cycle

A
  • Balance between hypothalamus nuclei and brainstem nuclei
  • Hypothalamus Nuclei
    • VLPO (Ventrolateral preoptic area)
      • Inhibits Tuberomammillary Nucleus
        • GABA
        • galanin
      • Brainstem Nuclei
        • Cholinergic nuclei
        • Locus Coeruleus
        • Raphe Nuclei
    • Orexin Nucleus
      • Hypothalamic neurons produce Orexin
        • Stimulates:
          • Tuberomammillary nucleus
          • cerebral cortex and basal forebrain
          • Raphe nucleus in brainstem
            • keep Brain awake
30
Q

Suprachiasmatic Nuclei

A

Suprachiasmatic Nucleus

  • control circadian rhythm
  • central pacemaker of circadian timing
    • receives direct input from the retina
    • sends oscillations to other areas of the brain ==>“Slave oscillators) in pineal gland
  • bilateral structure
  • anterior part of hypothalamus
  • Pathway:
    • Light hits the retina and stimulates photosensitive receptor ganglion cells
      • not rods and cones
    • send info to suprachiasmatic nucleus(hypothalamus)–> brainstem–> spinal cord–> intermedia lateral column–> enters Peripheral nervous system–>Superior Cervical Ganglion –> pineal gland
      *
31
Q

Sleep-wake cycle mechanism

A

2 parallel mechanisms

  • Homeostatic regulation (AKA sleep-wake homeostasis)
    • at the end of the day you feel tired and you want to get rest
    • homeostasis energy balance needs to be restored=SLEEP
  • Circadian regulation
    • stimulated by light cycle
    • light stimulates us to stay awake –>suprachiasmatic nucleus and pineal gland-Melatonin

Controlled by the:

  • hypothalamus
    • control homeostatic regulation
  • suprachiasmatic nucleus
    • control circadian rhythm
32
Q

EEG during different stages of sleep

A
33
Q

EEG during first hour of sleep

A
  • General Trend: from stage to stage
    • Desynchronized activity
    • as we fall asleep=brain activity Slower
      • Smaller Hz
      • Smaller Frequency
      • Higher Amplitude
  • Awake stage
    • Beta activity
    • first 15 mins
  • Stage I
    • 15-25 mins
  • Stage II
    • 25-35 mins
    • Sleep Spindles
  • Stage III
    • 35-50 mins
  • Stage IV
    • Delta activity
    • 50-60 mins
  • REM Sleep
    • 65+ mins
    • Aka Paradoxical sleep
    • rapid eye movement
34
Q

Pattern of night sleep

A
  • Initially:
    • Very long delta sleep stage
  • As you sleep more hours,
    • delta sleep decreases
    • Incrase in REM sleep
  • Morning hours
    • mostly REM sleep
  • Always cycle throughout the night
    • several points of REM and deep sleep
35
Q

Physiological changes during various sleep states

A
  • REM sleep
    • rapid eye movment
    • Early morning hours: EEG=lower activity
      • muscle paralysis
      • relaxed
    • Increases:
      • Heart Rate
      • Blood Pressure
      • Respiration
    • Penile errection (early morning)
36
Q

Areas of the brain that are activated or inactivated during REM sleep?

A
  • Activated:
    • Anterior Cingulate COrtex
    • Amygdala
    • Parahippocampal gyrus
    • Pontine Tegmentum
  • Inactive:
    • Posterior CIngulate cortex
    • Dorsolateral prefrontal cortex
37
Q

ARAS: NTs during different stages of sleep

A
  • Awake:
    • ARAS=ALL active: All excitatory
      • Acetylcholine
        • Colinergic nuclei
      • Glutamate
      • Norepinephrine
        • Locus COerulus
      • Serotonin
        • Raphe nuclei
      • Orexin
        • Tuberomammilary nuclei
  • SLow-Wave Sleep
    • All have reduced output
      • Acetylcholine
      • Norepinephrine
      • Serotonin
  • REM:
    • All reduced except Acetylchoine
    • Acetylcholine-active
      • Cholinergic Nuclei
      • PGO Waves
  • REM Sleep off:
    • Norepinephrine active
      • Locus coruleus
38
Q

Pattern of sleep throughout life

A
  • Sleep less as we age
  • embryo/babies-sleep the most
  • Total Sleep time:
    • Decreases then plateaus (6.5 hours)
  • REM sleep:
    • decreases, then plateaus, then rapidly declines
    • reduces more than any other stage
    • decreases as we age
  • Stage 4 slow wave
    • high in younger people
    • slowly decreases
  • Childhood:
    • long delta sleep and REM
  • Adulthood:
    • Decreased delta and REM sleep
  • Elderly
    • Continues to decrease
    • Parts of delta sleep almost missing
39
Q

Drugs and sleep

A
  • Barbituates
    • reduces delta sleep
    • No influence on REM sleep
    • Chronic use:
      • no Delta or REM sleep
  • Benzodiazepines
    • Reduces Delta sleep and REM sleep
  • Caffeine
    • reduces Delta and REM Sleep
40
Q

Sleep during Drug withdrawal

A
  • Rapid Increase in REM sleep
    • strong REM rebound
41
Q

Sleep Related Disorders

A
  • Insomnia
  • Sleep apnea
  • Sleep paralysis
  • Parasomnias
  • Narcolepsy
  • Restless leg syndrome
42
Q

Insomnia

A
  • Unable to fall asleep or get enough sleep
  • Affects 20% of people
  • triggered by stress
  • results in worrying that inhibits proper sleep
43
Q

Sleep apnea:

A
  • Lapses of breathing during sleep
    • mainly during REM sleep
  • connected to:
    • obesity
    • snoring
  • Results in being tired during the day
44
Q

Sleep Paralysis

A
  • Common but rare as a severe disorder
  • occurs during sleep when a person partially awakens but is unable to move
  • Can be frightening
  • nor dangerous
45
Q

Parasomnias

A
  • Class of disorders which includes:
    • nightmares
    • sleep walking
    • sleep talking
    • Wetting the bed
    • Grinding
    • Night terrors
46
Q

Night terrors vs Nightmares

A

Night Terrors:

  • occur during non-REM sleep
  • intense
  • less recall of dream content
  • panic/screaming/heart pounding
47
Q

Function of sleep and Dreaming

A
  • Not known
  • Hypothesis:
    • conservation of metabolic energy
    • thermoregulation
    • neural maturation
    • memory and cognition
48
Q

How do we diagnose epilepsy?

A

EEG only

Week 29 (1 decks)

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