Lecture on physiology of sleep and EEG for undergraduate and postgraduate medical colleges.

1. Electroencephalogram
-EEG
Dr.mrs.Minakshi Ashok Randive
Professor & Head

2. EEG
• 1- Introduction
• 2 - Significance
• 3 - Method of Recording
• 4 - Waves of EEG
• 5 - a - Alpha rhythm, b - Beta rhythm,c- Delta

3. Introduction
• Recording of electrical activity of brain is called
as EEG .
• Due to large number of Neurons & Synapses ,
electrical activity of the brain is complicated.
• Hans Berger had analysed the EEG waves
systematically primarily .
• EEG waves are referred as Bergers waves

4. Significance
• EEG is useful in diagnosis of Neurological
disorders and sleep disorders .
• Epilepsy - excessive discharge of impulses from
cerebral cortex .
• Subdural hematoma - collection of blood in
subdural space .
• Midbrain disorders - affecting ascending reticular
activating system .

5. Method of recording EEG
• It is recorded by placing electrodes on the Skull.
• Two types of Electrodes - unipolar & bipolar
• Bipolar - Both the terminals are placed in different parts
of the Brain .
• Unipolar - active electrode is placed in brain and the
indifferent electrode is kept on some part of the body
away from the cortex .
• The electrodes are connected to the recording device like
polygraph to record EEG .

6. Waves of EEG
• EEG has three frequency bands
• 1 - Alpha rhythm
• 2 - Beta rhythm
• 3 - Delta rhythm
• Next slide contains diagram of EEG waves , where
the frequency is different than the slides.
• Source of the slide is given on the slide itself .

7. –Johnny Appleseed
“Type a quote here.”

8. Alpha Rhythm
• Rhythmical oscillations in electrical potential appearing
at a frequency of 8 to 12 waves/second .
• Amplitude - 50 mV
• Obtained in inattentive brain , drowsiness , light sleep
or narcosis with closed eyes.
• Diminished when eyes are opened .
• These waves mostly marked in Parieto - Occipital area
.

9. Alpha Block
• When eyes are opened , Alpha rhythm is
replaced by fast ,irregular ,low voltage activity
with no dominant frequency . ( desynchronised )
• Any form of sensory stimulation , mental
concentration .

10. Beta rhythm
• Frequency - High - 15 to 60 /second .
• Low amplitude - 5 to 10 micro volt .
• Recorded during - mental activity, mental tension
or arousal state .

11. Gamma rhythm
• Higher mental activities or peak performance
state like problem solving , fear - very high
frequency waves of 30 to 100 / second .
• Some scientists consider these waves as Beta
rhythm .

12. Delta rhythm
• Low frequency high voltage waves at the rate
1 to 5 /second .
• Amplitude - 20 to 200 micro volt
• Common in early chield hood during waking
hours .
• In Adults it appears mostly during deep sleep .

13. Delta rhythm
• In adults other than sleep it appears in
pathological conditions - like Tumor ,Epilepsy
,Increased Intracranial pressure, mental
Depression .

14. Theta waves
• These appear in children below 5 years of age .
• Low frequency and low voltage waves .
• Frequency - 4 to 8 /second .
• Amplitude - 10 micro volt .

15. Physiology of sleep
• The mental and physical relaxation either
superficially or deeply with closed eyes is called
as Sleep .

16. Sleep requirement
• 1 - Newborn infants - 18 to 20 hours
• 2 - Growing children - 12 to 14 hours
• 3 - Adults - 7 to 9 hours
• 4 - Old persons - 5 to 7 hours

17. Types of Sleep
• 1 - Rapid Eye Movement sleep or REM sleep .
• 2 - Non Rapid Eye Movement sleep or NREM .

18. REM Sleep
• In this type - Rapid conjugate movement of the
eye balls occur frequently .
• The sleep is deep so also called as Paradoxical
sleep .
• It occupies about 20 to 30 % of sleeping period .
• Plays important role in consolidation of Memory .
• Dreams occurs in this phase .

19. NREM Sleep
• Eyeballs do not move .
• Also called as Slow wave sleep .
• Dreams do not occur .
• Occupies 70 to 80 % of Total sleeping period .
• It is followed by REM sleep .

20. Stages and EEG pattern
• REM sleep - EEG shows Irregular waves with
high frequency and low amplitude .
• Desynchronised waves .

21. NREM Sleep
• Based on EEG pattern NREM sleep is decided in
to four stages .
• Stage 1 - drowsiness - Alpha waves are
diminished and abolished .
• EEG shows only low voltage fluctuations and
infrequent Delta waves .

22. NREM Sleep
• Stage 2 - stage of light sleep
• Characterised by spindle bursts at frequency of
14 /second , superimposed by low voltage Delta
waves .

23. NREM Sleep
• Stage 3 - stage of Medium Sleep
• The spindle burst disappear .
• Frequency of Delta waves decreases to 1 or 2
per second .
• Amplitude increases to about 100 micro volts .

24. NREM Sleep
• Stage 4 - stage of deep sleep
• Delta waves become more prominent with low
frequency and high Amplitude .

25. Mechanism of sleep
• Sleep is induced by the stimulation of sleep
inducing centres in the brain .
• Damage to these centers results in
sleeplessness or persistent wakefulness called
Insomnia .

26. Sleep centers
• 1 - Raphe Nucleus
• 2 - Locus Ceruleus of Pons
• Raphe Nucleus - situated in lower Pons and
medulla , activation results in NREM sleep due to
release of Serotonine by nerve fibres arising .

27. Sleep centres
• Locus ceruleus of Pons - activation produces
REM sleep due to release of Noradrenaline .

28. Ascending Reticular
Activating System
• ARAS is responsible for wakefulness due to its
afferent and efferent connections with cerebral
cortex .
• Inhibition of ARAS induces sleep .
• Lesion leads to permanent Somnolence ( Coma
).

29. Physiological changes during
Sleep
• Most of the functions of the body are reduced to the
Basal levels .
• CVS - Heart rate reduces , 45 to 60 / min .
• Systolic Blood Pressure reduces to 90 to 110 mmHg .
Lowest level is reached about 4th hour of sleep and
remains at this level till a short time before waking up .
• During horrified dreams pressure is elevated above
130 mmHg .

30. Physiological Changes
• Plasma volume - volume decreases by 10 % .
• Respiratory system - respiratory rate and force
are decreased .
• G I system - salivary secretion decreases ,
contraction of empty stomach are more vigorous
• Excretory system - urine formation decreases .
• Sweat secretion - increases

31. Physiological changes
• Lacrimal secretion - decreases
• Muscle tone and Reflexes - muscle tone reduces
• Babinski sign becomes positive
• Knee jerk abolished
• Threshold of most of the reflexes increases
• Pupils are constricted
• Eye balls movement
• Muscle tone is decreased and it is called as sleep paralysis .

32. Sleep Disorders
• Insomnia - inability to sleep , it occurs due to
systemic illness or due to psychiatric problems ,
drug or alcohol addiction .
• Hypersomnia - excessive sleep due to lesion in
the in the floor of 3rd ventricle , brain tumours ,
encephalitis , myxedema , diabetes insipidus ,

33. Sleep disorder
• Narcolepsy and Cataplexy - these both are
hypothalamic disorders . Narcolepsy is sudden
attack of uncontrollable sleep .
Cataplexy - is the sudden outburst of emotion .
• Nightmare - it is condition extreme uneasiness or
discomfort or frightful dreams . It occurs mostly
during REM sleep . It occurs mostly due to
improper food intake , digestive disorder , nervous
disorder , it also occurs during drug or alcohol
withdrawal .

34. Sleep Apnea Syndrome
• Temporary stopage of breathing during sleep .
• Apnea is due to decreased stimulation of
Respiratory centers, arrest of diaphragmatic
movements , airway obstruction , when breathing
stops the resultant hypercapnia and hypoxia
stimulate respiration .
• Sleep apnea is seen in - obesity ,enlargement of
tonsil , myxedema , lesion in brainstem

35. Sleep Apnea Syndrome
• Common Features - loud snoring , nocturnal
insomnia , daytime sleeplessness , restless
movements , headache , fatigue .
• In severe conditions - hypertension and right heart
failure.
• Night Terror - it is common in children , child
awakes screaming in state of fright and semi
consciousness . Child can not recollect the attack
in the morning . It occurs during NREM sleep .

36. Dr. Minakshi Randive
“Thanks for patient listening ”