EEG waves and sleep cycle

1. EEG & SLEEP
MARYAM JAMILAH BINTI ABDUL HAMID
082013100002
IMS BANGALORE

2. LEARNING OUTCOME
• Electroencephalogram (EEG)
– Definition of EEG
– Type of waves
– Physiological basis
• SLEEP
– Definition of sleep
– EEG changes during sleep
– Classification of sleep
– Sleep cycle

3. ELECTROENCEPHALOGRAM (EEG)
• Introduced by Hans Berger
• Definition:
The record of electrical activity of the
cerebrum
Source of EEG
Rhythmically
discharging cell
bodies in the most
superficial layers of
the cortical grey
matter

5. • Two methods:
– Bipolar method
• Potential difference between two cortical electrodes
– Unipolar method
• Potential difference between an active cortical electrode
and an indifferent electrode

6. TYPE OF WAVES
EEG
Rhythm
Frequency
(Hz)
Amplitude
(μV)
Associated features
α 8-12 50-100
Present max in occipital & parieto-
occipital areas when eyes are closed
β 14-30 5-10
Generally seen in frontal region (normal
awake pattern); commonly seen in infants
θ 4-7 10
Often found over the parietal & temporal
areas (in children and early sleep)
δ 1-4 20-200
Usually appear during sleep.
Overbreathing or evidence of organic
brain disease (awake state)

7. Frequency
(Hz)
Amplitude
(μV)
8-12 50-100
14-30 5-10
4-7 10
1-4 20-200

8. FACTORS AFFECTING FREQUENCY
Frequency decreased Frequency increased
Low blood glucose level High blood glucose level
Low body temperature Rise in body temperature
A high arterial pCO2 A low arterial pCO2
Low levels of adrenal glucocorticoid
hormones
High levels of adrenal glucocorticoid
hormones
Anaesthesia or analgesia Alert state
Sleep Forced overbreathing

9. Alpha-block / Desynchronization of EEG
 Closing or not closing the eyes
 ALERT
 Pattern of EEG:
 Fast
 High frequency
 Irregular amplitude
 Also known as alerting response

10. PHYSIOLOGICAL BASIS OF EEG
1. Synchronizing
mechanisms
– Synchronizing effect
on each unit of activity
in its neighbors
– Rhythmic discharge of
impulses from the
thalamus
2. Desynchronizing
mechanism
– Stimulate specific sensory
system up to level of the
midbrain
– High-frequency stimulation of
the reticular formation
(midbrain tegmentum) & non-
specific projection nuclei of
the thalamus

11. Physiological process by which bodily
functions are periodically rested

12. EEG CHANGES DURING
SLEEP

13. PHYSIOLOGICAL CHANGES DURING SLEEP
1. CVS: Heart rate, cardiac output, vasomotor tone &
blood pressure
2. Respiratory system: Tidal volume, respiratory rate &
pulmonary ventilation
3. BMR: by 10-15%
4. Urine: Volume . Phosphate & specific gravity
5. Secretions: Salivary & lacrimal secretion but sweat

14. 6. Muscles: completely relax or tone is minimum
7. Eyes: eye ball roll up, drooping of upper eyelid, pupils
constrict
8. Blood volume:
9. Nervous system: EEG δ-wave, deep reflex reduced,
superficial reflex unaffected, vasomotor reflex brisk and
light reflex retained

15. CLASSIFICATION OF SLEEP
1. Non-rapid eye movement sleep (NREM)
2. Rapid eye movement sleep (REM) or Paradoxical
Sleep

16. NREM
• A recurring sleep state during which rapid eye
movements do not occur and dreaming does not occur;
accounts for about 75% of normal sleep time
• Tone: muscle tone decrease
• Eyes: rolling movement until they finally stop in stage 4
(deep sleep) with eyes turned upwards
• GH and GnRH: Pulsatile release
• CVS: BP, heart rate & respirstion

17. STAGES IN NREM
STAGE BEHAVIOURAL OBSERVATION EEG CHANGES
1
Light sleep:
a) Easily aroused by moderate
stimuli or even by neck muscle
jerks triggered by muscle stretch
receptors as head nods
b) Continuous lack of awareness
in α–wave amplitude &
frequency
2
True sleep:
Further lack of sensitivity to activation
and arousal
Appearance of sleep
spindles; bursts of regular
waves (frequency 14-15 Hz,
50μV) of a few seconds
duration.
-due to reverberating activity
between thalamus & cerebral
cortex

18. STAGE BEHAVIOURAL OBSERVATION EEG CHANGES
3 Sleep deepens
Sleep spindles (occasional)
now superimposed on a
background of δ waves type
(frequency 1-2 Hz & 100 μV
amplitude
4
Deep sleep:
a) Activation and arousal occurs only
with vigorous stimulation (high
threshold of awakening)
b) When awaken, person does not
report dreaming
Slow high voltage δ waves

19. REM
• Eyes: Saccadic eye movement
• Tone: Muscle tone (skeletal muscle) reduced; snoring
• Dreaming is closely associated
• CVS: Increase and irregularity of BP, heart rate &
respiratory rate
• Bruxism in children
• Erection of penis, engorgement of clitoris and twitches of
facial or limb muscles
• Ponto-Geniculo-Occipital (PGO); hypotonia

20. STAGE BEHAVIOURAL OBSERVATION EEG CHANGES
REM
Sleep
Deepest sleep
a) Greatest relaxation & difficulty of
arousal
b) Skeletal muscle tone is markedly
reduced except in the eye where
REM occurs
c) When awakened, subject reports
80-90% of the time that they have
been dreaming
Resembles that of alert
awake state; rapid low
voltage, irregular waves
(Desynchronized EEG)

21. SLEEP CYCLE
• Consist of two phases:
– NREM sleep followed by REM sleep
• Average total sleep period: 4-5 cycles, each lasting
90 to 100 minutes
• NREM: 80%
REM: 20%
• In neonates: 50% of NREM & 50% of REM
• REM sleep increases towards the morning

22. GENESIS OF SLEEP
Genesis of NREM
2 factors:
 Inhibition of reticular activating system (RAS) inputs
 Stimulation of sleep promoting mechanism
(diencephalic sleep zone & medullary synchronizing
zone)

23. Genesis of REM
2 factors:
 Discharge of norepinephrine (NE) from neurons in
pontine reticular formation & locus ceruleus
 PGO spikes; discharge of cholinergic neurons
 shifting NREM sleep to REM sleep

24. CONTROL OF SLEEP-WAKING CYCLE
Neural Mechanism
• Circadian rhythm consist typically 8 hours sleep (NREM
& REM alternate) and 16 hours awake
• It’s controlled by the hypothalamic suprachiasmatic
nucleus
• Sleep-waking cycle involve two interacting systems in
the brain stem; an arousal system & a sleep
producing system.

25. Mechanism that activates:-
Arousal system Sleep producing system
Stimulation of sensory receptors
Removal of afferent stimuli;
decrease activity of RAS
Stimulation of midline reticular
formation of the brain stem,
hypothalamus and locus ceruleus
Stimulation of hypothalamic areas
(anterior and posterior)
Stimulation of raphe nuclei

26. Humoral/Chemical mechanism
• Sleep-inducing chemical substances:
– Norepinephrine
– Serotonin
– Acetylcholine
– Hypotoxin
– Delta-sleep inducing peptide (DSIP)
– Sleep promoting factor (factor S)

28. CONCLUSION
Conclusion:
EEG and Sleep are described.

29. REFERENCES
• AK JAIN, MEDICAL PHYSIOLOGY,
THIRD EDITION
• GUYTON & HALL, SOUTH ASIA EDITION
• http://catalystathletics.com/articles/article.p
hp?articleID=1845