Download SLEEP AND EEG

Lecture – 3
Dr. Zahoor Ali Shaikh
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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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
It is awareness of external world or
surrounding.
Level of Consciousness (states in decreasing
order)
 Maximum alertness
 Wakefulness
 Sleep
 Coma
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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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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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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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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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Two types of Sleep
i). NREM Sleep or slow wave sleep
ii). REM sleep or paradoxical sleep
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They are characterized by different EEG
patterns and different behavior.
We will discuss each one.
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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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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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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 1020mins episode of REM or paradoxical sleep.
A person has 5-6 cycles of sleep i.e. NREMREM again NREM-REM throughout the night.
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Sleep pattern in young adult
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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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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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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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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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EEG Recording From Normal Adult Male
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rhythmic, 8-13 Hz
mostly on occipital lobe
20-200 μ V
normal,
relaxed awake rhythm with eyes closed
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irregular, 14-30 Hz
mostly on temporal and frontal lobe
Recorded during mental activity, awake
person
excitement
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rhythmic, 4-7 Hz
Stage II and Stage III sleep
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slow, < 3.5 Hz
Stage III, IV sleep
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NREM SLEEP
Stage I – characterized by low amplitude, high
frequency EEG activity.
Stage II – slow waves theta (θ)
Stage III - Theta (θ) - Delta(δ) waves
Stage IV – Delta(δ) waves
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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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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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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 brainstem.
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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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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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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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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3. Sleep is necessary for learning and memory
This may explain Why infants need so much
sleep.
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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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EEG showing sleep spindle STAGE II
K - complex
Sleep Spindle
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Grandmal seizure
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Petitmal seizure
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THANK YOU
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