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.

• 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)

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.

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

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.


• 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)


• Best recorded from parietal & occipital regions.

• Thalamo-cortical connections are important for it.

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

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.

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.

Brain waves in normal E.E.G

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


• 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.


• Thalamo-cortical connections are important, mainly in recording of alpha waves.

• If these fibers are cut, alpha waves disappear & delta waves appear.

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.


• 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.


• 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.


• E.E.G silence is sure indication of brain death.

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.

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

• 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.

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

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

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.

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

• Of muscle contrations throughout the opposite side of body.

• Beginning in mouth region and marching progressively downwards to legs.

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.

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.

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

Lack of SLEEP

If insomnia is further prolonged, person may develop:

• Dysarthria (defect of speech)

• Tremors

• Abnormal gait

Requirement of SLEEP

Varies with age:

• Infants: 20-24 hrs

• Young children: 12 hrs

• Young adults: 7-9 hrs

• Old age: 5-7 hrs

Relationship of SLEEP with ANS:

During sleep, generally there is

• Sympathetic inhibition &

• Parasympathetic stimulation

Types of SLEEP

• SLOW WAVE / Non-REM sleep / Delta wave sleep

• REM sleep / paradoxical sleep

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.

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

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.


• 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.


• 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.


• 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.


• 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.

Replacement of alpha rhythm by asynchronous rhythm on opening eye:

Types of SLEEP


• 75% sleep

• Dreaming without memory

• Increased parasympathetic stimulation

• Decreased muscle tone

• Bed-wetting in children


• 25% sleep

• Active dreaming with memory

• Increased sympathetic stimulation

• Increased muscle tone, muscle twitching & convulsions.

Types of SLEEP• 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


• 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


• Increased GH• No erection• No bruxism• Sleep walking


• Increased corticosteroid

• Erection• Bruxism• No sleep walking

Changes in EEG when a person goes to sleep:

Mechanism of sleep

• There is a cycle of wakefulness & sleep.

• When a person is awake, gradually neurons in reticular activating system become less & less active & there is also activation of certain sleep centers.

• This results into sleep.

Mechanism of sleep

• During hours of sleep, neurons in reticular activating system become progressively more & more active, leading to wakefulness.

Sleep centers:

• 1) LOCUS CERULEUS:

Location:• At junction of midbrain & pons.

• Neurons in this locus secrete nor epinephrine at nerve endings of nerve fibers.

• Nerve fibers from these neurons pass to reticular formation.

Sleep centers:

• This center (Locus Ceruleus) is involved in REM sleep, when brain is highly active.

• So perhaps nor-epinephrine secreting neurons are involved (sympathetic stimulation in REM sleep)

• Ach secreting neurons in reticular formation of upper brain-stem are also involved.

PGO spikes

• In REM sleep there are PGO spikes (large phasic potentials in groups of 3-5).

• These spikes are due to Acetylcholine secreting neurons in this pathway of producing REM sleep.

• Only the tone of neck muscles is dec., other muscles keep their tone.

• But at the same time there is locus ceruleus dependent inhibition of voluntary act.

Sleep centers:

• 2) RAPHE MAGNUS NUCLEUS:• Midline linear nuclei in upper pons & lower

medulla.• Fibers from here pass to reticular

formation, hypothalamus, limbic system & also spinal cord.

• These fibers synapse with pain-inhibitory neurons in dorsal horn of spinal cord (analgesia system).

Sleep centers:

• There is release of serotonin at nerve endings of these fibers.

• Raphe Magnus Nucleus is involved in Deep Slow Wave sleep (NREM sleep).

• Serotonin inhibitors wakefulness.

• Stimulation of SCN of Anterior hypothalamus, certain thalamic nuclei & portion of nucleus of tractus solitarius NREM sleep.

Muramyl dipeptide induced sleep:

Experimental observation:

• In animals kept awake for 2-3 days, muramyl dipeptide & other sleep promoting factors are produced in CSF of brain stem which can be later detected in blood & urine.

• When muramyl dipeptide is injected to some other animal, it immediately passes into sleep.

DISORDERS OF SLEEP:

• 1) Somnambulism / sleep walking

• 2) Bedwetting in children

• 3) Bruxism

• 4) Insomnia

• 5) Narcolepsy

• 6) Sleep apnea

1) Somnambulism / sleep walking• Occurs during slow wave sleep / NREM.

• More common in male children.

• Episode of sleep walking may remain for many minutes.

• Person walks with open eyes, obstacles are avoided during walking.

• Person wakes up unaware of sleep walking.

2) Bedwetting in children

• Also called Nocturnal enuresis.

• May be due to parasympathetic dominance, as it occurs in slow wave sleep.

3) Bruxism

• Teeth grinding

• Occurs during active sleep (REM sleep)

4) Insomnia

• Inability to sleep, although sufficient facilities & time is available for sleep.

• Reason: Psychological or medical.

5) Narcolepsy:

• There are attacks of intense desire to sleep during day time

• Person cannot resist to sleep in the day

• Attack may last for seconds to minutes

Cause of Narcolepsy:

Etiology:

• Considered to be hypothalamic disorder

Evidence:

• Other features of hypothalamic disorders are present, e.g., obesity, polyuria, sexual retardation.

6) Sleep apnea

• During sleep, breathing stops suddenly.

• May be repeated 100’s of times in severe cases.

• When breathing stops, person wakes up, takes a few breaths & then tries to go to sleep.

6) Sleep apnea

• In the morning, person is fatigued & drowsy.

• There may be features of respiratory failure without respiratory disease.

6) Sleep apnea

ETIOLOGY:

• Exact cause ??

POSSIBLE CAUSES:

• Obesity

• Airway obstruction

• Disease of CNS

Story of sleep disorders:• Somoo (somnambulism / sleep walking) knocks mom’s

bedroom door, while sleeping.

• Complains of wetting his bed (bed-wetting)

• Mom reacts by Bruxism / teeth grinding

• Mom shouts: You disturbed my sleep, I cannot sleep at night because of you!! (insomnia)

• Mom adds: I will now go to sleep at my work place in the day! (narcolepsy)

• Mom continues: I am so tired, that I can hardly breathe (sleep apnea)

EEG & Sleep

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