Download SLEEP AND EEG

Lecture – 14
Dr. Zahoor Ali Shaikh
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What is Sleep ?
 Sleep is a state when person is not aware of
surrounding. 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 input.
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
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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
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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


We spend 80% time in NREM sleep and 20%
time in REM sleep.

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.
During these stages ( I- IV) there is progressive
slowing of EEG waves and EEG waves
become high amplitude, hence it is called
Slow wave sleep.
 NREM 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 .

After Stage I to IV of NREM sleep, we get 1020 mins episode of REM or paradoxical sleep.

Then we reverse to NREM – REM cycle again.
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
A person has 5-6 cycles of sleep i.e. NREM-REM,
again NREM-REM throughout the night.

Time for each stage of sleep during one cycle:
Stage I – 3-5% [5-10mins]
Stage II – 50-60% [30-40mins]
Stage III & IV – 10-20% [10-20mins]
REM sleep – 10-20% [10-20mins]

Note – Time for REM sleep increases during each
cycle.
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Sleep pattern in young adult
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


During REM sleep, rapid eye movement
occur.
Muscle tone throughout body is decreased
EEG pattern during REM cycle abruptly gets
similar to that of wake, alert person, although
person is in sleep, therefore, it is called
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 spend more time in REM sleep.
New born sleeps about 16-20 hrs/day.

In children, NREM and REM become 50%
each.
During childhood, child sleeps 10-15 hrs/day.
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
Adult person needs 6-9 hours of sleep. He
spends 80% time in NREM sleep and 20% in
REM sleep

In elderly NREM Stage IV (deep sleep) and REM
sleep decreases. Old person sleeps 5-6 hrs
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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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
German physiologist and psychiatrist Hans Berger
recorded the first human EEG in 1924.

It is one of the most remarkable development in
the history of clinical neurology
Hans Berger
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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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
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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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


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irregular, 14-30 Hz
mostly on temporal and frontal lobe
Recorded during mental activity, awake
person (eyes open).
excitement
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
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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 – high frequency EEG activity alpha,
replaced by slower waves
Stage II – slow waves theta (θ)
Stage III - Theta (θ) - Delta(δ) waves
Stage 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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
Night mares occur in stage III and IV.

People especially children walk and talk during
stage III and IV.

Dream occur during REM sleep.
Brain imaging during REM sleep shows increase
activity in visual area and limbic system and
decreased activity in Prefrontal area reflecting
dreams are related to emotional memory bank but
not to thinking.
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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.
 During Sleep 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).
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
During sleep , Adenosine level decreases 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 insomnia
- cause of Insomnia- 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.


Sleep Apnea syndrome - person not breathing for a
while, snoring , obesity, little sleep.
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EEG
Machine
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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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
EEG is useful in diagnosis of
1. Epilepsy
2. Sleep Disorders
3. Brain death [used in some centers]
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
Polysomnography is a series of tests
performed on a patient with sleep disorders
e.g. sleep apnea, narcolepsy

It is over night procedure and includes
monitoring of ECG, blood pressure, air flow,
blood oxygen level, EEG, eye movements,
and movements of respiratory muscle and
limbs
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THANK YOU
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