This document provides information about electroencephalography (EEG). It discusses the significance of EEG in diagnosing neurological and sleep disorders. It describes how EEG is recorded by placing electrodes on the skull. It outlines the different waves seen on EEG including alpha, beta, delta, theta, and gamma rhythms. It also discusses the physiology and stages of sleep as well as common sleep disorders like insomnia, hypersomnia, narcolepsy, sleep apnea, and night terrors. Physiological changes that occur during sleep like reductions in heart rate, blood pressure, respiration are also summarized.

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 ”