1 / 71

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.

ballari-taj
Download Presentation

EEG & Sleep

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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

More Related