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Lecture – 3 Dr. Zahoor Ali Shaikh. SLEEP AND EEG. SLEEP. What is Sleep ? Sleep is active process. It consist of two processes. 1. Non-Rapid Eye Movement (NREM) or slow wave sleep 2. Rapid Eye Movement (REM) or paradoxical sleep. What is Consciousness?. - PowerPoint PPT Presentation
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SLEEP AND EEGLecture – 3Dr. Zahoor Ali Shaikh
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SLEEP
What is Sleep ? Sleep is active process. It consist of
two processes. 1. Non-Rapid Eye Movement
(NREM) or slow wave sleep 2. Rapid Eye Movement (REM) or
paradoxical sleep
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What is Consciousness?
It is awareness of external world or surrounding.
Level of Consciousness (states in decreasing order)
Maximum alertness Wakefulness Sleep Coma
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Level of Consciousness
Maximum alertness It depends on high activity level of
central nervous system, reticular activating system (RAS).
Wakefulness Awake person is aware of
surrounding.
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Level of Consciousness
Sleep Sleep is an active process, brain overall activity is
not reduced. Sleeping people are not consciously aware of
surrounding, but they have inward conscious experience e.g. dreams.
They can be aroused by external stimuli e.g. alarm.
Coma It is total unresponsiveness of a living person to
external stimuli due to brain damage that interferes with RAS or severe depression of cerebral cortex.
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RETICULAR FORMATION
What is Reticular Formation? It is network of interconnected neurons,
which run through the entire brain-stem and into the thalamus.
Reticular formation receives all incoming sensory synaptic input.
Ascending fibers originating from reticular formation carry signals upwards to arouse and activate the cerebral cortex. These fibers are called Reticular Activating System.
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Reticular Activating System
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RETICULAR FORMATION
RAS controls the cortical alertness. Fibers descending from cortex
especially motor cortex can activate RAS.
Centers that govern sleep are within the brain-stem, but recent evidence suggest that the center for slow sleep (NREM) lie in the hypothalamus.
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SLEEP
Two types of Sleep i). NREM Sleep or slow wave sleep ii). REM sleep or paradoxical sleep
They are characterized by different EEG patterns and different behavior.
We will discuss each one.
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i). NREM Sleep or slow wave sleep
Slow wave sleep has four stages. Each stage showing progressively
slower EEG waves of high amplitude, hence it is called Slow wave sleep.
Stages are called: Stage I Stage II Stage III Stage IV
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NREM Sleep or slow wave sleep
Stage I At one set of sleep, Stage I is referred
as drowsiness or pre-stage of sleep.
Stage II Light sleep.
Stage III and IV Deep sleep
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NREM Sleep or slow wave sleep At one set of sleep, we move from light
sleep of Stage I to deep sleep of Stage IV during a period of 60-70mins then we reverse through the same stages.
After Stage I to IV of NREM sleep, we get 10-20mins episode of REM or paradoxical sleep.
A person has 5-6 cycles of sleep i.e. NREM-REM again NREM-REM throughout the night.
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Sleep pattern in young adult
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REM SLEEP
During REM sleep, rapid eye movement occur, it occupies 20% of total sleep time in adult person.
EEG pattern during REM cycle abruptly gets similar to that of wake, alert person although person is still in sleep, therefore, we call it paradoxical sleep (person sleeping but EEG pattern is like awake person).
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EEG during different types of sleep
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SLEEP
Infants spent more time in REM sleep. In children, NREM and REM become
50% each. New born sleeps about 16-20 hrs/day. During childhood, child sleeps 10
hrs/day. Adult person needs 7-8 hours of sleep
In elderly NREM, Stage IV (deep sleep) and REM sleep decreases.
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Electroencephalogram
What is EEG? 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.
We record EEG with electrodes over the scalp.
We record different types of waves during different stages of sleep.
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Generation of large EEG signals by synchronous activity
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EEG Waves recorded are
Alpha wave -- 8 – 13 Hz. Beta wave -- >13 Hz. (14 – 30 Hz.) Theta wave -- 4 – 7.5 Hz. Delta waves – 1 – 3.5 Hz.
D T A B
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Different types of brain waves in normal EEG
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EEG Recording From Normal Adult Male
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Alpha wave
rhythmic, 8-13 Hz mostly on occipital lobe 20-200 μ V normal, relaxed awake rhythm with eyes
closed
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Beta wave
irregular, 14-30 Hz mostly on temporal and frontal lobe Recorded during mental activity,
awake person excitement
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Theta wave
rhythmic, 4-7 Hz Stage II and Stage III sleep
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Delta wave
slow, < 3.5 Hz Stage III, IV sleep
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EEG WAVES DURING DIFFERENT STAGES OF SLEEP NREM SLEEPStage I – characterized by low amplitude, high
frequency EEG activity.Stage II – slow waves theta (θ) Stage III - Theta (θ) - Delta(δ) wavesStage IV – Delta(δ) waves
REM Rapid low voltage, EEG activity like stage I of NREM. Eye movements are recorded. Person is in deep sleep, difficult to wake.
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BEHAVIORAL PATTERN DURING SLEEP
Night measure occur in stage III and IV.
People especially children walk and talk during stage III and IV.
Dream occur during REM sleep.
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THANK YOU
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SLEEP WAKE CYCLE
Sleep wake cycle is controlled by three neural system.
1. Arousal system – regulated by group of neuron in hypothalamus and involves reticular activating system (RAS) originating in brain-stem.
2. Slow wave sleep center (NREM) – In the hypothalamus, it has neurons that induce sleep.
3. REM sleep center in the brain-stem – it has neurons which become active during REM sleep
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FUNCTIONS OF SLEEP
What is Function of Sleep? It is not clear. We spend 1/3 of our life
sleeping. Sleep is not accompanied by reduction in
neural activity (brain cells are not resting) but there is change in the activity.
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What is the purpose of NREM and REM sleep?
Theories are 1. During metabolic activity of neuron and glial cells,
Adenosine is produced from the ATP during awake state (increased adenosine when we are awake more).
Adenosine inhibits arousal center, this can bring NREM sleep (injection of adenosine induces normal sleep).
Adenosine level decreases during sleep as brain uses this adenosine for replenishing its limited energy stores.
Caffeine blocks adenosine receptors in the brain, therefore causes wakefulness.
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What is the purpose of NREM and REM sleep?
2. Restoration and recovery proposal During awake, brain neuron release
neurotransmitter Norepinephrine and Serotonin.
But during REM sleep, these neurotransmitters are not released, therefore, it restores receptor sensitivity.
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What is the purpose of NREM and REM sleep?
3. Sleep is necessary for learning and memory
This may explain Why infants need so much sleep.
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SLEEP DISORDERS
Insomnia - Insomnia is difficulty in getting sleep - 10-15% of population suffer from it - cause of Insomnia- difficult to find may be
anxiety, too much coffee, tea, soft drink, stimulants, drugs travelling .
Narcolepsy Rare disorder affects 0.5% population. Person suddenly falls asleep at odd
moments. May occur frequently throughout the day.
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EXTRA INFORMATION
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10 /20 % system of EEG electrode placement
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Sleep Spindle
K - complex
EEG showing sleep spindle STAGE II
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Grandmal seizure
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Petitmal seizure
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POLYSOMNOGRAM SLEEP STUDY
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Polysomnographic Record
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THANK YOU