Sleep Physiology & EEG (Electroencephalogram)

Sleep & EEG
Prof. Dr. Rashid Mahmood

©Prof. Dr. Rashid Mahmood
Sleep & EEG
Sleep
The Electroencephalogram
EEG (Brain Waves)
214-Dec-17

3
About sleep?
• Why is sleep important for life? Is it essential for life?
• What is sleep? Is it a different type of brain activity or just “Rest of
neurons”?
• Have you seen rapidly moving eyes of a sleeping person?
• What is the effect of sleep on HR, BP, RR etc?
• “Wetting bed at night” is a urinary bladder disorder or sleep disorder?
• Do you walk during sleep?
• Is it difficult to arouse you early in the morning? Why?
• Why elderly people sleep less?
• What is the effect of depression on sleep and how then sleeping pills
work? ©Prof. Dr. Rashid Mahmood Sleep & EEG14-Dec-17

Objectives
• Goal/Aim:
• To understand the physiology of EEG waves and sleep
• Specific Objectives: At the end of the lesson student will be
able to:
• Describe the primary types of rhythms that make up
electroencephalogram (EEG).
• Define sleep and name its types
• Summarize the characteristics of each type of sleep
• Describe the Sleep-Wakefulness cycle.
• Describe the mechanism of sleep genesis
• List sleep abnormalities
4©Prof. Dr. Rashid Mahmood Sleep & EEG14-Dec-17

Lesson Contents
• Functions of Sleep
• EEG
• Brain waves vs Brain Activity
• Sleep
• Basic Theories of Sleep
• Sleep-Wakefulness Cycle
• Physiological Effects of Sleep
514-Dec-17

Functions of Sleep
•To restore natural balances among the
neuronal centers
1. Neural maturation
2. Facilitation of learning or memory (consolidation)
3. Cognition
4. Clearance of metabolic waste products generated by
neural activity in the awake state
5. Conservation of metabolic energy (maintenance of
Metabolic-Caloric Maintenance)
6. Thermal equilibrium
7. Immune Competence 6

7
•Definition ?
•Record of variations in brain potential
•Where to place Electrodes ?
•Scalp (unopened skull)
•On the brain
•In the brain
•Unipolar or bipolar ?
•Both
The Electroencephalogram
©Prof. Dr. Rashid Mahmood Sleep & EEG14-Dec-17

8
Brain waves in normal EEG
Name the waves of
EEG
14-Dec-17

Question No.1
• Write any TWO functions of Sleep.
©Prof. Dr. Rashid Mahmood Sleep & EEG 914-Dec-17

Rhythms of EEG (Waves)
1. Alpha Rhythm
i. At what state of
consciousness it is
generally recorded?
ii. Is it regular or
irregular?
iii. Frequency?
i. Awake
At rest
Mind wandering
Eyes closed (not
focusing/ dim
light)
Disappear during
deep sleep
ii. Regular
iii. 8 – 12 Hz
10©Prof. Dr. Rashid Mahmood Sleep & EEG14-Dec-17

11
Alpha rhythm
in different
species

12
2. Beta Rhythm
1. At what state of consciousness it is
generally recorded?
2. Amplitude?
3. Frequency?
Alpha
Block by
olfactory
stimulus
1. Extra activation of CNS
2. Tension
 Lower amplitude
 Higher frequency (18 – 30 HZ)

13
• 3. Theta Rhythm
1. Children
2. Light sleep
3. Extremely relaxed
4. Drowsy
5. Emotional stress in some
adults
• Disappointment
• Frustration
6. Degenerative brain states
• Large amplitude
• Slow (4 – 7 HZ)
• Regular
I. At what state of
consciousness it is
generally
recorded?
II. Amplitude?
III. Frequency?
IV. Regular ?
3. Theta Rhythm

14
• Deep sleep
• Infancy
• Serious organic brain disease
• Highest voltage
• Lowest frequency (< 4/sec)
• regular
i. At what state
of
consciousnes
s it is
generally
recorded?
ii. Amplitude?
iii. Frequency?
iv. Regular ?
4. Delta Waves

15
•5. Gamma Oscillation
•Highest frequency (30 – 80 HZ)
•Focusing (deep) attention on something

16
Brain waves in normal EEG
Sleep & EEG
14-Dec-17

17
Brain waves vs Brain Activity
Alert wakefulness : Beta waves
Quiet wakefulness : Alpha waves
Focusing attention : Gamma waves
Light Sleep : Theta waves
Deep sleep : Delta waves

Effect of various degrees of cerebral
activities on basic rhythms of EEG

Uses of EEG
1. Diagnosis of cerebral function
Epilepsy
2. Legal determination of brain death
Medical, legal & social implications
3. Distinguish various stages of sleep
14-Dec-17 ©Prof. Dr. Rashid Mahmood Sleep & EEG 19

Question No.2
• A person who was awake, at rest, with mind wandering
and eyes closed is suddenly given an olfactory
stimulus. What Rhythm of EEG (Waves) was he having,
and it changed to what Rhythm of EEG?

SLEEPConsciousness :
Awareness of one’s
existence,
thoughts and
Surroundings
Sleep :
an unconsciousness
from which the person
can be aroused by
sensory or other stimuli

22
Types of Sleep
(Non-Rapid Eye Movement & Rapid Eye Movement)
1. NREM (slow wave sleep)  75 %
Characteristics:
1. Deep restful
2. 4 stages (Stage 1,2,3,4)
3. EEG: High amplitude slow waves
4. Dreamless sleep
5. Body movements, like change of side
6. Decrease vegetative functions
B.P, R.R, B.M.R, Peripheral Vascular Tone

23
Sleep
2. REM Sleep (Desynchronized)
 5 – 30 min
 Every 90 min
 Duration decrease with deep sleep
Characteristics:
1. Active dreaming
2. Difficult to arouse (morning)
3. Decreased or absent muscle tone
4. H.R, R.R irregular
5. Few irregular muscles movements (eyes)
6. Active brain
7. EEG: Rapid, low voltage

Hypnogram
2414-Dec-17

26
Progressive
changes in the
characteristics
of the brain
waves during
different stages
of wakefulness
and sleep
Sleep & EEG14-Dec-17

Question No.3
• What is the effect of REM sleep on muscle tone?

28
Basic Theories
•Passive theory
•Active inhibitory process
•Sub-cortical

29
Genesis of NREM Sleep
Stimulation of synchronizing regions:
1. Basal fore-brain sleep zone:
• Raphe nuclei in lower half of pons and medulla
• Serotonin
2. Medullary synchronizing zone:
• Reticular formation of medulla at level of tractus solitarius
Contd…

30
3. Diencephalic sleep zone:
• Posterior Hypothalamus
• Intralaminal and anterior Thalamic nuclei
• Mechanism:
• Low / high frequency stimulation
• Mechano-receptor stimulation
• Regular repeated monotonous stimulation
Genesis of NREM Sleep

31
Genesis of REM Sleep
•Large Acetylcholine secreting neurons
•Pontine reticular formation

Sleep-Wakefulness Cycle
Sleep Centers
Not Activated
No inhibition
of RAS
Active
RAS
+ve feedback
from cerebral
cortex and
PNS
Fatigue of
neurons of
RAS ??
Breaking of
+ve feedback
Active
inhibitory
process of
RAS
Sleep
Fatigue of
Active
inhibitory
process of
RAS
Sleep & EEG
32
Circadian
Rhythm
Role of
Melatonin
14-Dec-17

33
Neurotransmitters
1. Sleep peptide
2. Serotonin (NREM)
3. Muramyl peptide
4. Adenosine (Vs. caffeine)
5. PGD2 (Vs. PG E2)
6. Orexin (Hypocretin) (Hypothalamus)
7. Acetylcholine (REM)

34
Sleep Cycle at
various ages
(REM is indicated
by darker areas)
Hypnogram
©Prof. Dr. Rashid Mahmood Sleep & EEG
14-Dec-17

35
Changes in human sleep
pattern with age

36
Physiological Effects of Sleep
•Nervous system
•Other structures
Sleep & EEG
14-Dec-17

37
Sleep
Disorders
•Insomnia
• Fatal familial insomnia
•Parasomnias
• Nocturnal enuresis (bed wetting)
• Night terrors
• Somnambulism (Sleep walking)
•Narcolepsy
• Cataplexy
•Obstructive Sleep apnea (OSA)
•REM behavior disorder
•Periodic Limb Movement Disorder
(PLMD) ©Prof. Dr. Rashid Mahmood
Sleep & EEG
14-Dec-17

Question No.4
• What is the effect of REM sleep on HR, BP, and RR ?

• The Electroencephalogram is the Record of variations in brain
potential
• Brain waves in normal EEG include Alpha, Beta, Theta, Delta and
Gamma
• Sleep is an unconsciousness from which the person can be aroused
by sensory or other stimuli
• Types of sleep include NREM (slow wave sleep) and REM Sleep
(Desynchronized) sleep.
• Basic Theories of sleep include Passive theory, Active inhibitory
process, and Sub-cortical theory
• Neurotransmitters involved in the process of Sleep include Serotonin,
Muramyl peptide, Adenosine ,PGD2, Acetylcholine, and Orexin
• Melatonin and Circadian Rhythm are important for Sleep-Wakefulness
Cycle
©Prof. Dr. Rashid Mahmood Sleep & EEG 39
Take home points

Learning resources
• Guyton and Hall (Text book of physiology), 13th Edition
• Human Physiology : from cells to system Lauralee Sherwood,9th Edition
• Masood Ahmed Khan (Neurophysiology for Medical students, 3rd edition)
• Lecture Notes on Neurophysiology by Prof. M. Tariq (2nd edition)
• Suggestions for improvement in 3rd Edition invited

Questions?
Comments?
drrashid62@gmail.com
rashid.mahmood@rmc.edu.pk
Also available at slideshare.com

Sleep Physiology & EEG (Electroencephalogram)

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