SLEEP AND EEG

DR NILESH KATE
MBBS,MD
ASSOCIATE PROF
ESIC MEDICAL COLLEGE, GULBARGA.
DEPT. OF PHYSIOLOGY
SLEEP AND
ELECTROENCEPHA
LOGRAM

OBJECTIVES.
 Electrical activity of the brain.
 Evolked cortical potential
 Electroencephalogram
 Wakefullness and sleep.
 Wakefullness
 Neural substrate
 Chemical mediators.
 Sleep

ELECTRICAL ACTIVITY OF THE
BRAIN.
 Evolked cortical
potential.
 Primary Evolked
potential.
 Diffuse secondary
response.
Wednesday, April 25, 2018

EVOLKED CORTICAL
POTENTIAL.
 Surface electrical
activity recorded from
scalp in response to
specific & adequate
stimulus.
 Electrical activity of
2 types.

PRIMARY EVOLKED
POTENTIAL.
 Initial brief & localized
response over the
specific sensory cortex.
 Characterized by
 Latency – 5-12 ms
 Surface positive followed
by negative wave.
 Highly specific in its
location.

DIFFUSE SECONDARY
RESPONSE.
 Latency – 20-80 ms
 Positive negative wave
sequence larger & more
prolonged.
 Not highly localized.

TYPES OF EVOLKED
POTENTIAL.
 Depending on type of
stimulus.
 Visual Evolked potential.
(VEP)
 Brain stem auditory
Evolked potential
(BAEP)
 Somatosensory Evolked
potential.
 Event related
potentials.

TYPES OF EVOLKED
POTENTIAL.
 Depending on
latency of
response.
 Stimulus related
potentials.
 Event related
Evolked potential.

STIMULUS RELATED
POTENTIALS.
 Series of waves relates to
sensory modality.
 Early latency response –
latency < 10ms
 Mid-latency response –
Latency 10-50 ms.
 Long latency response –
latency > 50 ms.

EVENT RELATED EVOLKED
POTENTIAL.
 Dependent on subject’s
attention & level of
arousal.
 Related to cognitive
events associated with
distinction of target
from non- target
stimuli.

CLINICAL USES OF EVOLKED
POTENTIALS.
 Stimulus related Evolked potential – Reflects
functional integrity of sensory pathway.
 So any defect is shown by delayed peak or Interpeak
latencies.
 Event related Evolked potential.
 Related to cognitive behavior.
 By use of ERP clinical assessment of Dementia &
Delirium is well established.

ELECTROENCEPHALOGRAM
 Introduced by German
Psychiatrists Hans
Berger.
 Record of spontaneous
electrical activity of
brain taken from
surface of scalp.

ELECTROENCEPHALOGRAM
 The wave oscillations differ
in frequency & amplitude
in different points on scalp
& during mental alertness.
 Frequency – range 1-50
cycles/sec.
 Amplitude – 50-200 μV.
 Irregular & without any
pattern.

WAVES OF EEG
 Alpha waves
 Beta waves.
 Theta waves.
 Delta waves.

ALPHA WAVES
 Most prominent
 Person awake, quiet at rest
, eyes closed.
 Characteristic features.
 Frequency – 8-13 Hz.
 Amplitude – 50 μV.
 Location – Parito-occipital
area.
 Disappear – During sleep.

ALPHA WAVES
 Causes of decreased
frequency.
 Old age, decreased
cerebral metabolism
 Low BSL
 Low body temp
 Low adrenal
Glucocorticoids.
 High arterial Pco2
 Sleep.
 Causes of increased
frequency.
 Alpha block – α waves
attenuates & replaced by
fast ,irregular & low
amplitude waves. Occurs in
 Open eyes
 During conscious mental
activities.
 During aroused & alerting
response.

BETA WAVES.
 CHARACTERISTIC
FEATURES.
 Location – Parietal &
frontal area.
 Appear – Tension & CNS
activation.
 Arousal response
 Infants & Barbiturates.

THETA WAVES.
 CHARACTERISTIC
FEATURES.
 Amplitude – 10 μV.
 Location – Temporal &
Parietal region in children.

THETA WAVES.
 Do not in normal waking
individuals (except in
Newborn)
 Seen in emotional states
like Disappointment &
Frustration.
 Many brain disorders.
 Increased during crying
in children.

DELTA WAVES.
 CHARACTERISTIC
FEATURES.
 Frequency – < 4 Hz.
 Location – Strictly in
cortex.

DELTA WAVES.
 CHARACTERISTIC
FEATURES.
 Do not occur in normal
waking individuals but
seen in
 Deep sleep (stage III &
IV of NREM)
 Infancy
 Serious brain damage.

NEUROPHYSIOLOGICAL BASIS
OF EEG.
 Cortical Grey matter along with its thalamic
connections are mainly responsible for Rhythmic
discharge of cells & EEG.
 Current flow in the fluctuating dipoles.
 Dendrites are sites of polarizing & Hyperpolarizing
local potential change.

NEUROPHYSIOLOGICAL BASIS
OF EEG.
 So cell dendrite relationship is constantly shifting
dipole.
 So becomes sites of current sink.
 EEG is due to Graded potentials which are post
synaptic potentials in Brain neurons.

SYNCHRONIZING
MECHANISMS.
 Rhythmic discharge from thalamus.
 Synchronizing activity of neighboring cells due to
 Effect of parietal neural process to each other.
 Interconnections of neurons by Inhibitory pathway.

DESYNCHRONIZING
MECHANISMS.
 α block – replacement
of rhythmic EEG pattern
with irregular low
voltage activity.
 Due to sensory
stimulation of RAS.

VARIATION IN EEG WAVE
FORMATION WITH AGE.
 In Infants – occipital
rhythm is slow(0.5 Hz)
than Adults (8-13 Hz).
 In children occipital
rhythm speeds up & adult α
pattern gradually appears
in adolescence.
 After 15 years EEG
waveforms become same
as adults.

ABNORMAL EEG WAVEFORMS
 1 Epilepsy.
 Idiopathic abnormal
waves as spike, sharp
wave & spike & slow
wave complex.
 Between abnormal
irregular slow wave
appears.

TYPES.
 GRANDMAL EPILEPSY
– Serious fits
accompanied by
convulsions with tonic
muscle contraction,
clonic jerks & loss of
consciousness.
 EEG shows continuous
spike or sharp waves.

TYPES
 PETITMAL EPILEPSY –
Sudden loss of consciousness
for few sec without
convulsions with local
twitching.
 PSYCHOMOTOR EPILEPSY –
Typical fit with inappropriate
movements with
hallucinations without loss of
consciousness.

 2 Consciousness Dysfunction – slow wave
appears.
 Disturbance of consciousness in coma, stupor &
syncope.

 3 Organic brain Dysfunction – when brain
functional trouble occurs – no wave is generated
from that part but slow wave is generated from
surrounding organization.

 4 Brain Death –
Individual delclared
dead when brain cells
stop activity, EEG waves
becomes flat in all
channels & finally
disappears.

WAKEFULLNESS
 The RAS of Reticular
formation is the neural
substrate of the
consciousness & sleep
waking cycle.

NEURAL SUBSTRATE FOR
WAKEFULLNESS.
 Reticular activating system. – Responsible for
tonic maintenance of cortical activation &
Behavioural arousal of wake fullness.
 Thalamus – VM, Intra-laminar & Midline nuclei are
involved in activation of entire cerebral cortex.

NEURAL SUBSTRATE FOR
WAKEFULLNESS.
 Hypothalamus and
sub thalamus.
 Basal forebrain –
Mainly Nucleus Basalis
of Meynert, Nuclei of
Diagonal band &
septum.
 It receives impulses from
Reticular formation.

CHEMICAL MEDIATORS OF
WAKEFULLNESS
 Neurotransmitters.
 Cerebrospinal fluid
borne peptides.
 Blood borne
peptides.

NEUROTRANSMITTERS.
 Catecholamines – NE neurons of locus Coeruleus &
Brain stem project diffusly to forebrain & cortex
play an imp role
 Acetylcholine - – Cholinergic agonists &
anticholinesterase promote cortical activation &
wakefulness.

NEUROTRANSMITTERS.
 Histamine – Arousing effect produced by
intraventricular administration of Histamine
 Sedative effect produced by Antihistaminics.
 Glutamate- Excitatory Neurotransmitters released
from cerebral cortex in highest quantities in cortical
activation.

CEREBROSPINAL FLUID
BORNE PEPTIDES.
 Substance P
 Hypothalamic
releasing factors.
 Vasoactive intestinal
peptides.

BLOOD BORNE PEPTIDES.
 Epinephrine &
histamine – Do not cross
BBB but act on
circumventricular organ.
 Glucocorticoids – these
readily cross BBB.

SLEEP
 State of
Unconsciousness from
which person can be
aroused by sensory or
other stimuli.

SLEEP WAKE CYCLE AND
FACTORS AFFECTING SLEEP.
 Control of sleep wake cycle.
 Sleep wake cycle –
endogenous
 Biological clock – in
Suprachiasmatic Nucleus of
Anterior Hypothalamus.
 Zeitgebers – Time givers;
Most imp is sunlight
through
Retinohypothalamic tract.

FACTORS AFFECTING SLEEP.
 Darkened room
 Comfortable surrounding
temperature
 Silence
 Physical & mental
relaxation.
 Consumption of basic urge
 Low frequency stimulation.

TYPES AND STAGES OF SLEEP
 Non-REM sleep.
 REM SLEEP.
ALTERNATE IN A
SLEEP CYCLE.

TYPES AND STAGES OF SLEEP
 Non-REM sleep – Non
rapid eye movement
sleep (slow wave
sleep)
 Sleep begins with
Non-REM.

STAGES AND EEG PATTERN OF
NON-REM SLEEP.
 Stage of wakefulness –
state of wakefulness &
consciousness due to RAS
stimulation to cortex.
 EEG – Low amplitude β
waves.
 Stage of quiet, awake rest
with eyes closed.
 Highly synchronized large α
waves

STAGE OF NON-REM SLEEP.
 Stage 1 – low amplitude
mix frequency activity.
 Stage 2 – Stage of light
sleep, sleep spindles
appears.
 These are bursts of α
like 10-14 Hz, 50 μv
waves.

STAGE OF NON-REM SLEEP.
 Stage 3 – Stage of
Moderate deep sleep
 High amplitude slow
waves i.e. δ waves
 Stage 4 – Deep sleep
 Dome like very slow,
large waves called δ
waves
 Characterized by Marked
synchronization.

PHYSIOLOGICAL CHANGES
DURING NON-REM SLEEP
 Muscle tone
 Heart rate & BP
 Respiratory rate
 Body metabolism
 Eyes – slow rolling movements
until finally stop in stage 4 with
eyes turned upwards.
 Pituitary pulsatile release of
growth hormones & Gonadotropins
– slows down.

BEHAVIORAL CHANGES
 Consciousness – progressively reduced.
 Resistance to be awakened increases.
 When awake do not report Dreaming.
 Discriminate response to meaningful & non
meaningful stimuli.

INTELLECTUAL FUNCTIONS
DURING NON-REM SLEEP.
 Thoughts becomes
illogical & Incoherent
towards sleep.
 Retrograde Amnesia.
 Sleep inactivates
consolidation of short
term to long term
memory

REM SLEEP
 RAPID EYE
MOVEMENT SLEEP /
FAST WAVE SLEEP /
Paradoxical sleep /
Deepest sleep /
Dream sleep.

EEG PATTERN OF REM SLEEP.
 High frequency low
amplitude pattern ( β
rhythm)
 So also called
Desynchronized or fast
wave sleep.
 More difficult to awake in
REM than Non-REM
 EEG Pattern of Wakefulness
- Paradoxical

PHYSIOLOGICAL CHANGES
 Rapid Eye Movement
 HR & RR – Irregular.
 Muscle tone – reduced.
 Twitching of limb.
 Middle ear muscles active
 Penile erection in males & Engorgement of Clitoris in
females.
 Impaired Thermoregulation
 Teeth Grinding.

BEHAVIORAL CHANGES
DURING REM SLEEP
 Arousal –
 Difficult to arouse
 But when awakened
immediately alert &
aware
 Dreaming occurs
 80% - vivid dreams
recall.

SLEEP CYCLE.
 Average sleep period of
7-8 hr divided into 5
cycles of Non-REM &
REM, alternate with
each other.

SLEEP CYCLE.
 Duration of sleep cycles and sleep stages.
 Avg duration of each cycle – 90 min.
 In 1st
cycle 85 min is NREM & 5 min REM.
 25% of entire sleep is in REM.
 NREM decreases & REM increases in further cycles.

VARIATIONS IN SLEEP CYCLES.
 In adult sleep starts with REM in special
conditions as
 Jet lag, Chronic sleep deprivation, narcolepsy, acute
withdrawal of REM suppressing drugs, endogenous
depressions.

VARIATIONS IN TOTAL SLEEP
DURATIONS.
 Avg sleep time per day
 Infant – 16hrs.
 Childhood -10 hrs
 Adulthood -7-8 hrs.
 Old age - < 8 hrs.

VARIATIONS IN TIME PERIOD OF
DIFFERENT STAGES OF SLEEP.
 Effect of AGE.
 Premature infant – 80% in REM
 Full term infant – 50 % in REM.
 In adulthood reduction in total sleep time to 8 hrs.(2
REM; 6 NREM)

GENESIS OF SLEEP
 Genesis of Non-REM sleep.
 Genesis of REM sleep.

GENESIS OF NON-REM SLEEP.
 Diencephalic sleep zone
 Sleep fascilitatory center – Ant Hypothalamus.
 Sleep inhibitory center – Post Hypothalamus.
 Medullary synchronizing zone
 Basal forebrain sleep zone.

ACTIVITY OF NON-REM ON
CELLS
 Mechanism of production of sleep spindles and
slow waves of Non-REM sleep.
 These synchronized synaptic potentials are rhythmic
firing of thalamic relay neurons to cortex.
 This rhythmic firing is due to GABAergic inhibitory
neurons in Nucleus Reticularis around thalamus.

GENESIS OF REM SLEEP.
 Role of cholinergic neurons of Mid-brain and the
adjacent dorsal Pons.
 Role of Nucleus Reticularis pontis oralis.
 Cholinergic PGO on cells.
 REM waking on cells.
 REM on cells.

CHEMICAL MEDIATORS OF
SLEEP
 Neurotransmitters – Include Serotonin,
Acetylcholine & Noradrenaline.
 Sleep producing substances are – Muramyl
Dipeptide (found in bacterial cell wall), Interleukin-
1, adenosine, Delta sleep inducing peptide, PGD2,
Argenine vasotoxin.

PHYSIOLOGICAL SIGNIFICANCE
OF SLEEP.
 Sleep may serve as a period of body’s rest and
metabolic restoration.
 Sleep is necessary for certain forms of learning.

PHYSIOLOGICAL SIGNIFICANCE
OF SLEEP.
 REM sleep is necessary for mental wellbeing.
 REM sleep plays an important role in homeostatic
mechanism.

SLEEP DISORDERS.
 Insomnia.
 Fatal familial
insomnia.
 Narcolepsy.
 Some sleep
disorders associated
with non-REM sleep
(slow wave sleep)

SLEEP AND EEG

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