EEG & Sleep

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

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

5. TYPE OF WAVES EEG Rhythm Frequency (Hz) Amplitude ( μ V) Associated features α 8-12 50-100 Present max in occipital & parieto -occipital areas when eyes are closed β 14-30 5-10 Generally s een 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)

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

7. 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 pCO 2 A low arterial pCO 2 Low levels of adrenal glucocorticoid hormones High levels of adrenal glucocorticoid hormones Anaesthesia or analgesia Alert state Sleep Forced overbreathing

8. 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

9. PHYSIOLOGICAL BASIS OF EEG Synchronizing mechanisms Synchronizing effect on each unit of activity in its neighbors Rhythmic discharge of impulses from the thalamus 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

10. Physiological process by which bodily functions are periodically rested SLEEP

11. EEG CHANGES DURING SLEEP

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

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

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

15. 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

16. STAGES IN NREM STAGE BEHAVIOURAL OBSERVATION EEG CHANGES 1 Light sleep : Easily aroused by moderate stimuli or even by neck muscle jerks triggered by muscle stretch receptors as head nods 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, 50 μ V) of a few seconds duration. -due to reverberating activity between thalamus & cerebral cortex

17. 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 μ V amplitude 4 Deep sleep : Activation and arousal occurs only with vigorous stimulation (high threshold of awakening) When awaken, person does not report dreaming Slow high voltage δ waves

18. 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

19. STAGE BEHAVIOURAL OBSERVATION EEG CHANGES REM Sleep Deepest sleep Greatest relaxation & difficulty of arousal Skeletal muscle tone is markedly reduced except in the eye where REM occurs 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 )

20. 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

21. 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)

22. 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

23. 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 .

24. 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

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

26. CONCLUSION Conclusion: EEG and Sleep are described.

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