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EEG & Sleep

EEG & Sleep. EEG: definition. It is record of variations in brain potential It is record of electrical activity of brain/neurons in different phases e.g. during sleep, wakefulness and epilepsy. E.E.G. Carried out by placing electrodes on surface of scalp.

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EEG & Sleep

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  1. EEG & Sleep

  2. EEG: definition • It is record of variations in brain potential • It is record of electrical activity of brain/neurons in different phases e.g. during sleep, wakefulness and epilepsy.

  3. E.E.G • Carried out by placing electrodes on surface of scalp. • Sometimes placed directly on surface of cerebral cortex, e.g., during neurosurgical operations or in experimental animals. • Such a record is called Electro- Corticogram (ECOG)

  4. E.E.G • E.E.G was 1st recorded by a German Psychiatrist Hans Berger. • There are 2 methods for EEG recording • Recording of EEG can be unipolar or bipolar. • In unipolar EEG, active electrode is placed on surface of scalp, while inactive or indifferent is placed at a distant point, like tip of 7th cervical vertebra. • In bipolar EEG, both electrodes are active & placed on surface of scalp.

  5. E.E.G • In routine E.E.G, 20 electrodes are placed on scalp at different points to record EEG. • In normal EEG, 4 types of waves can be seen: alpha, beta, theta & delta, in different phases. • Character of each wave is described as • 1- its intensity/voltage 2- frequency

  6. Alpha waves: Waves of quiet wakefulness / waves of inattentiveness: • Frequency: 8-13 / sec • Voltage: 50 micro-volts • Relaxed awareness These are recorded when a person is awake but mentally relaxed & inattentive, e.g., lying comfortably in a quiet room, eyes are closed & person is mentally relaxed & inattentive.

  7. Alpha waves: Waves of quiet wakefulness / waves of inattentiveness: • When a person opens eyes or the brain becomes active by thinking process or solving a problem, alpha waves disappear. • Frequency of alpha waves decreases by decreased body temperature, decreased glucocorticoid secretion, hypoglycemia & increase in pCO2. (due to cold temp. / empty stomach / during suffocation, one cant relax)

  8. Alpha waves: Waves of quiet wakefulness / waves of inattentiveness: • Best recorded from parietal & occipital regions. • Thalamo-cortical connections are important for it.

  9. Beta waves: waves of alertness / wakefulness / desynchronized waves • Frequency: 14-80 cycles/sec • Amplitude / voltage: 20 microvolts. Awareness with concentrated attention • Recorded when brain is highly active. • Best recorded from parietal & frontal regions. • Recorded during REM sleep. • Appear on eye opening

  10. Theta waves: • Frequency: 4-7 / sec • Voltage: 10 microvolts • Best recorded from parietal & temporal regions. • Recorded during light sleep. • Recorded in adults during states of frustration & disappointment. • In children normally recorded in awake E.E.G. • Also recorded in brain disorders like Grand Mal Epilepsy. In degenerative brain disorders.

  11. Delta Waves: • Very slow waves. • Frequency: 0.5 - 3 / sec • Voltage: 100 microvolts • Recorded in deep & restful sleep. • Also recorded in coma, general anesthesia & in epilepsy. In organic brain disorders.

  12. Brain waves in normal E.E.G

  13. Physiological basis of E.E.G: • Electrical activity recorded in EEG, is mainly from superficial layers of cerebral cortex which have number of dendrites on which many nerve terminals synapse. • Some terminals are excitatory (EPSP is produced), some are inhibitory (IPSP is produced). • Electrical activity recorded in EEG, is summation of EPSPs & IPSPs

  14. Physiological basis of E.E.G: • Amplitude of waves in EEG depends on how much the waves are synchronized / coordinated. • If waves are synchronized, there is increased amplitude. • If desynchronized, there are deflections in different directions & these neutralize each other, resulting into a small amplitude like in beta waves. • During each wave there is synchronous discharge/ activation of neurons.

  15. Physiological basis of E.E.G: • Thalamo-cortical connections are important, mainly in recording of alpha waves. • If these fibers are cut, alpha waves disappear & delta waves appear.

  16. Clinical use of E.E.G: • EEG reflects functional state of brain. • Recorded as an investigation in patients . • Also recorded for research purpose. • Recorded for many hours in epilepsy cases. • EEG machines are now computerized & there is automatic analysis of EEG.

  17. Clinical use of E.E.G: • Helps to diagnose SOL (Space occupying lesion) in skull, which may be infective, neoplastic, traumatic or vascular. • It helps in diagnosis of epilepsy & its types. • It helps in diagnosis of psychopathic disorders.

  18. Clinical use of E.E.G: • In Grand Mal epilepsy, there may be theta or delta waves (high voltage waves) in EEG. • In Petit Mal epilepsy, there is spike & dome pattern. • In Psychomotor epilepsy, mainly delta waves are seen.

  19. Clinical use of E.E.G: • E.E.G silence is sure indication of brain death.

  20. Epilepsy • Epilepsy (also called “seizures”) is characterized by uncontrolled excessive activity of either part or all of CNS. • Attack occurs when basal level of excitability of neurons crosses threshold. • Epilepsy can be classified into three major types: • grand mal epilepsy, petit mal epilepsy, and focal epilepsy.

  21. Grand Mal Epilepsy/Generalized epilepsy • Grand mal epilepsy is characterized by extreme neuronal discharges in all areas of the brain  cerebral cortex, deep parts of cerebrum, and brain stem. • Discharges transmitted into the spinal cord sometimes cause generalized tonic seizures of the entire body, followed by alternating tonic and spasmodic muscle contractions called tonic-clonic seizures

  22. person bites his tongue • difficulty in breathing & cyanosis • urination and defecation can occur • grand mal seizure lasts from a few sec to 3 to 4 min. It is also characterized by post seizure depression of the entire nervous system.

  23. Factors which produce epilepsy • Strong emotional stimuli • Hyperventilation or alkalosis • Effects of some drugs e.g. phenylenetetrazole • High fever • Loud noises • Bright light • Traumatic lesion in any part of brain

  24. Petit mal/Partial epilepsy • Person suddenly becomes unconscious. • Convulsions do not occur • Muscles of face show twitching & blinking of eyes • Afterwards person become normal • It occurs in late childhood • Absence syndrome/ absence epilepsy • Excitatory thalamocortical neurons

  25. Focal Epilepsy • It involves only localized area of brain (cerebral cortex or deep parts of cerebrum) • The abnormality starts from a particular area and spreads to the adjacent area.

  26. Focal Epilepsy • Two types • 1- Jacksonian epilepsy • 2- Psychomotor epilepsy • Causes • 1- scar tissue in brain, 2- Tumor, 3- some destroyed part of brain tissue • In Jacks, as the wave of excitation spreads over motor cortex, it causes progressive march

  27. Of muscle contrations throughout the opposite side of body. • Beginning in mouth region and marching progressively downwards to legs.

  28. Psychomotor epilepsy • It is characterized by emotional outburst such as abnormal rage,anxiety,fear or discomfort. • There is amnesia or confused mental state for some period. • The cause, are the abnormalities in temporal lobe & tumor in hypothalamus and limbic system.

  29. SLEEP • “Period of inactivity during which there is unconsciousness from which person can be aroused by sensory & other stimuli”. • Unconsciousness during surgical anesthesia, epilepsy & coma should not be considered as sleep.

  30. Lack of SLEEP • Sleep is essential for normal life. • It restores a balance between different parts of nervous system. If a person is not allowed to sleep for 2-3 days, certain effects are seen: • Loss of concentration • Slow thought making • Loss of memory • irritability

  31. Lack of SLEEP If insomnia is further prolonged, person may develop: • Dysarthria (defect of speech) • Tremors • Abnormal gait

  32. Requirement of SLEEP Varies with age: • Infants: 20-24 hrs • Young children: 12 hrs • Young adults: 7-9 hrs • Old age: 5-7 hrs

  33. Relationship of SLEEP with ANS: During sleep, generally there is • Sympathetic inhibition & • Parasympathetic stimulation

  34. SLOW WAVE / Non-REM sleep / Delta wave sleep REM sleep / paradoxical sleep Types of SLEEP

  35. SLOW WAVE / Non-REM sleep / Delta wave sleep • Deep & restful sleep. • If a person is tired, he passes into deep sleep in 1 hr. • On average it constitutes 75% of total sleep during a night. • Dreams can be seen but are not remembered, so cannot be recalled. • Muscle tone decreases.

  36. SLOW WAVE / Non-REM sleep / Delta wave sleep • Slowing of heart rate & respiratory rate • BMR decrease • There is GH secretion • Pupillary constriction. • Sleep walking (somnambulism) may be seen during slow wave sleep

  37. REM sleep / paradoxical sleep • Occurs in periods lasting for 5-30 min. • Each period is repeated at every 90 min. • There are 4-6 periods of REM sleep during a night. • It constitutes 25% of total night sleep.

  38. REM sleep / paradoxical sleep • Its duration is different in different age groups. • There is more REM sleep as age advances. • If a person is tired, less REM sleep at night. • If a person has taken rest during day time, more REM sleep at night.

  39. REM sleep / paradoxical sleep • There is active dreaming & dreams can be recalled. • It is difficult to arouse the person from REM sleep as compared to non REM sleep but • Usually in the morning, person wakes up from REM sleep.

  40. REM sleep / paradoxical sleep • During REM sleep, brain is highly active, so beta waves are recorded from EEG. • Muscle tone increases. • Rapid movement of eye. • Twitching in different parts of body. • Mild convulsions.

  41. REM sleep / paradoxical sleep • Respiratory & heart rate becomes irregular during REM sleep. • Increased secretion of corticosteroid hormones. • In males, may be erection (parasympathetic stimulation) • Teeth grinding (BRUXISM) occurs. • Replacement of alpha rhythm by asynchronous rhythm on opening eye.

  42. Replacement of alpha rhythm by asynchronous rhythm on opening eye:

  43. SLOW WAVE / Non-REM sleep / Delta wave sleep 75% sleep Dreaming without memory Increased parasympathetic stimulation Decreased muscle tone Bed-wetting in children REM sleep / paradoxical sleep 25% sleep Active dreaming with memory Increased sympathetic stimulation Increased muscle tone, muscle twitching & convulsions. Types of SLEEP

  44. SLOW WAVE / Non-REM sleep / Delta wave sleep Decreased heart rate Decreased respiratory rate Pupil constriction Easy to arouse from sleep Brain is not active REM sleep / paradoxical sleep Irregular heart rate Irregular respiratory rate No constriction of pupil Difficult to arouse from sleep, but gets up spontaneously in the morning Brain is active Types of SLEEP

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