eeg, brain waves, seizures and sleep
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EEG, Brain Waves, Seizures and Sleep. Electroencephalography (EEG). Electro : relating to electricity. Encephalo : relating to the brain. Graphy : writing or representation produced in a specified manner. - PowerPoint PPT PresentationTRANSCRIPT
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EEG, Brain Waves, Seizures and Sleep
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Electroencephalography (EEG)
Electro: relating to electricity. Encephalo: relating to the brain. Graphy: writing or representation
produced in a specified manner.
Therefore, EEG produces a graphed representation of the electrical activity occurring in a person’s brain.
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Origin of EEG waves
EEG is the record of electrical activity of brain( superficial layer i.e. the dendrites of pyramidal cells) by placing the electrodes on the scalp.
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EEG Electrode Placement
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Classifying EEG brain waves Frequency: the number of oscillations/waves per second,
measured in Hertz (Hz) reflects the firing rate of neurons alpha, beta, theta, delta
Amplitude: the magnitude of brain waves, measured in millivolts (mV), gives an indication of the wave’s “power”. The number of neurons firing in synchrony & the distance
between the neurons and the recording electrode
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Delta Waves
Slowest frequency waves: 1 – 3 Hz
Associated tasks & behaviors: deep, dreamless sleep, not
moving, not attentive, sleeping
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Theta Waves Slow wave frequency: 4 – 8 Hz
Associated tasks & behaviors: State between wakefulness and sleep
“Drowsy” during sleep, meditation, internal focus, and
prayer; subconsciousness.
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Alpha Waves
Mid wave frequency: 8 - 13 Hz
Parietal and occipital lobes Associated tasks &
behaviors: Relaxing, watching television,
light reading (e.g., novel), eyes closed.
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Beta Waves High wave frequency: 12 - 35
Hz The “normal” dominant rhythm \ mostly on temporal and frontal
lobe Associated tasks &
behaviors: listening and thinking during
analytical problem solving, judgment, decision making, processing information,
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EEG Waveforms Alpha
8-13 Hz Parietal and occipital
prominent Relaxed wakeful
Beta 13-30 Hz Frontal prominent Intense mental activity
Delta 0.5-4 Hz Drowsiness/early SWS
Theta 4-7 Hz Drowsiness/early SWS
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Seizure Abnormal electrical
discharge. Initially synchronous May have no motor
component
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Convulsion Indicative of seizure
activity Motoric output of
synchronous neuronal firing.
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Primary (Idiopathic) Seizure Disorders
No identifiable cause
Not the result of overt disease or injury
In short, a guess.
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Secondary (Symptomatic) Seizure Disorders
Associated with or secondary to disease or injury
e.g. trauma, neoplasm, or infection.
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Epilepsy
Seizures and/or convulsions can be acute and isolated…
…they can be associated with a treatable organic disorder…
When seizures/convulsions are chronic and of undefined origin…
…the condition is described as epilepsy.
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Generalized Seizure Disorders
May be convulsive or not and include... Absence Myoclonic Clonic Tonic-Clonic
(Grand mal) Atonic
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Normal vs. Tonic-Clonic
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Normal vs. Absence
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Partial Seizure Disorders
Focal, localized seizures including... Simple
No impairment of consciousness. Complex
Consciousness impaired or disturbed. Secondarily generalized
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Normal vs. Partial
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Scheme of Seizure SpreadSimple (Focal) Partial
Seizures
Contralateral spread
From M.I. Davila-Garcia, HowardUniv., 2003
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Seizure Pathophysiology
Altered ionic conductance (increased excitability) of neuron.
Reduced inhibitory neuronal (primarily GABAergic) control.
Increased excitatory neuronal (primarily glutamatergic) control.
Probable mechanisms tend to overlap.
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Cellular and Synaptic Mechanisms of Epileptic Seizures
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Sleep
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Why Do We Need Sleep?
Adaptive Evolutionary Function safety energy conservation/ efficiency
Restorative Function body rejuvenation & growth
Brain Plasticity enhances synaptic connections memory consolidation
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The ascending arousal system promotes wakeA. B.
Modified from Fuller et al., J Biol Rhythms, 2006
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Hypocreatin (orexin)
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Narcolepsy VS Insomnia
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Melatonin: Produced by pineal gland, released at night-inhibited during the day (circadian regulation); initiates and maintain sleep; treat symptoms of jet lag and insomnia
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SCN lesioning
Tau mutant with period of ~20h
Wild type animal with period of ~24h
Transplanting SCN of donor with ~20-h period
Wild type animal acquiresperiod of donor (~20h)
SCN lesioning abolishes circadian rhythm
A
B
C
SCN and sleep
Modified from Ralph and Lehman, Trends Neuro 1991
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Coffee
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Coffee During waking, brain consume ATP
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Coffee During waking, brain consume ATP
adenosine
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Coffee During waking, brain consume ATP
adenosine
Adenosine bind to A1 receptor
Inhibit acetylcholine neurons
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Coffee During waking, brain consume ATP
adenosine
Adenosine bind to A1 receptor
Inhibit acetylcholine neurons
Caffeine and Theophylline are A1
antagonist
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Sleep stages
Awake Stage 1 Stage 2 Stage 3 Stage 4
Slow wave sleep
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Sleep stages
Awake Stage 1 Stage 2 Stage 3 Stage 4 Rapid eye movement
sleep (REM)
Slow wave sleep (NREM)
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Types and Stages of Sleep: NREM
Stage 1 – eyes are closed and relaxation begins; the EEG shows alpha waves; one can be easily aroused
Stage 2 – EEG pattern is irregular with sleep spindles (high-voltage wave bursts); arousal is more difficult
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–Stage 3 – sleep deepens;; theta and delta waves appear; vital signs decline; dreaming is common
–Stage 4 – EEG pattern is dominated by delta waves; skeletal muscles are relaxed; arousal is difficult
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REM Sleep Presence of beta activity (desynchronized EEG
pattern) Physiological arousal threshold increases
Heart-rate quickens Breathing more irregular and rapid Brainwave activity resembles wakefulness Genital arousal
Loss of muscle tone (paralysis) Vivid, emotional dreams May be involved in memory consolidation
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AFTER ROFFWARG , MUZIO & DEMEMT, Science (1966).
2
4
6
8
10
12
14
1650 yrs
90 yrs
33-45 yrs
19-30 yrs
14-18 yrs
10-13 yrs5-9 yrs
3-5 yrs
2-3 yrs
6-23 mos
3- 5 mos
1-15 days
NREM SLEEP
50 40 30 25 2018.5
2022
18.920-23
WAKINGREM SLEEP
14 13 12 11 10 8.5 7.75 7 6 5.75
24
0
SLEEP AND WAKETHROUGHOUT HUMAN LIFE
HO
UR
S P
ER
DA
Y
2
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REM Dreaming NREM Dreaming
“vivid and exciting”~3 per nightLonger, more
detailedFantasy worldnightmares
“just thinking”Shorter, less activeLogical, realistic
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Sleep Disorders
insomnia sleep walking, talking, and
eating nightmares and night terrors narcolepsy sleep apnea