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Lecture – 14 Dr. Zahoor Ali Shaikh. SLEEP AND EEG. SLEEP. What is Sleep ? Sleep is a state when person is not aware of surrounding. Sleep is active process. It consist of two processes. 1. Non-Rapid Eye Movement (NREM) or slow wave sleep - PowerPoint PPT Presentation

Transcript of SLEEP AND EEG


SLEEP AND EEGLecture 14Dr. Zahoor Ali Shaikh1SLEEPWhat is Sleep ?Sleep is a state when person is not aware of surrounding. Sleep is active process. It consist of two processes. 1. Non-Rapid Eye Movement (NREM) or slow wave sleep 2. Rapid Eye Movement (REM) or paradoxical sleep 2What is Consciousness?It is awareness of external world or surrounding.

Level of Consciousness (states in decreasing order)Maximum alertnessWakefulness SleepComa3Level of ConsciousnessMaximum alertness It depends on high activity level of central nervous system, reticular activating system (RAS).

WakefulnessAwake person is aware of surrounding.

4Level of ConsciousnessSleepSleep is an active process, brain overall activity is not reduced. Sleeping people are not consciously aware of surrounding, but they have inward conscious experience e.g. dreams. They can be aroused by external stimuli e.g. alarm.

ComaIt is total unresponsiveness of a living person to external stimuli due to brain damage that interferes with RAS or severe depression of cerebral cortex.

5RETICULAR FORMATIONWhat is Reticular Formation?

It is network of interconnected neurons, which run through the entire brain-stem and into the thalamus.

Reticular formation receives all incoming sensory input.6RETICULAR FORMATION [cont]Ascending fibers originating from reticular formation carry signals upwards to arouse and activate the cerebral cortex. These fibers are called Reticular Activating System.


Reticular Activating SystemRETICULAR FORMATIONRAS controls the cortical alertness.Fibers descending from cortex especially motor cortex can activate RAS.Centers that govern sleep are within the brain-stem, but recent evidence suggest that the center for slow sleep (NREM) lie in the hypothalamus.9SLEEPTwo types of Sleep i). NREM Sleep or slow wave sleep ii). REM sleep or paradoxical sleep

We spend 80% time in NREM sleep and 20% time in REM sleep.

They are characterized by different EEG patterns and different behavior.

We will discuss each one.10i). NREM Sleep or slow wave sleepSlow wave sleep has four stages.During these stages ( I- IV) there is progressive slowing of EEG waves and EEG waves become high amplitude, hence it is called Slow wave sleep. NREM Stages are called: Stage I Stage II Stage III Stage IV11NREM Sleep or slow wave sleepStage IAt one set of sleep, Stage I is referred as drowsiness or pre-stage of sleep.

Stage IILight sleep.

Stage III and IVDeep sleep12NREM Sleep or slow wave sleepAt one set of sleep, we move from light sleep of Stage I to deep sleep of Stage IV during a period of 60-70mins .

After Stage I to IV of NREM sleep, we get 10-20 mins episode of REM or paradoxical sleep.

Then we reverse to NREM REM cycle again.13NREM Sleep or slow wave sleepA person has 5-6 cycles of sleep i.e. NREM-REM, again NREM-REM throughout the night.

Time for each stage of sleep during one cycle: Stage I 3-5% [5-10mins] Stage II 50-60% [30-40mins] Stage III & IV 10-20% [10-20mins] REM sleep 10-20% [10-20mins]

Note Time for REM sleep increases during each cycle.1415

Sleep pattern in young adultREM SLEEPDuring REM sleep, rapid eye movement occur. Muscle tone throughout body is decreased

EEG pattern during REM cycle abruptly gets similar to that of wake, alert person, although person is in sleep, therefore, it is called paradoxical sleep (person sleeping but EEG pattern is like awake person).1617

EEG during different types of sleepSLEEPInfants spend more time in REM sleep. New born sleeps about 16-20 hrs/day.

In children, NREM and REM become 50% each. During childhood, child sleeps 10-15 hrs/day.

18SLEEPAdult person needs 6-9 hours of sleep. He spends 80% time in NREM sleep and 20% in REM sleep

In elderly NREM Stage IV (deep sleep) and REM sleep decreases. Old person sleeps 5-6 hrs

19ElectroencephalogramWhat is EEG?EEG is the record of electrical activity of brain (superficial layer i.e. the dendrites of pyramidal cells) by placing the electrodes on the scalp.We record EEG with electrodes over the scalp.We record different types of waves during different stages of sleep.

20ElectroencephalogramGerman physiologist and psychiatrist Hans Berger recorded the first human EEG in 1924.

It is one of the most remarkable development in the history of clinical neurology 21

Hans BergerEEG Electrode Placement22

EEG Waves recorded areAlpha wave -- 8 13 Hz.Beta wave -- >13 Hz. (14 30 Hz.)Theta wave -- 4 7.5 Hz.Delta waves 1 3.5 Hz.D T A B23Different types of brain waves in normal EEG24

EEG Recording From Normal Adult Male25Alpha waverhythmic, 8-13 Hzmostly on occipital lobe20-200 Vnormal,relaxed awake rhythm with eyes closed

26Beta waveirregular, 14-30 Hzmostly on temporal and frontal lobeRecorded during mental activity, awake person (eyes open).excitement

27Theta waverhythmic, 4-7 HzStage II and Stage III sleep

28Delta waveslow, < 3.5 HzStage III, IV sleep

29EEG WAVES DURING DIFFERENT STAGES OF SLEEPNREM SLEEPStage I high frequency EEG activity alpha, replaced by slower wavesStage II slow waves theta () Stage III - Theta () - Delta() wavesStage IV Delta() waves

REMRapid low voltage, EEG activity like stage I of NREM.Eye movements are recorded.Person is in deep sleep, difficult to wake.30BEHAVIORAL PATTERN DURING SLEEPNight mares occur in stage III and IV.

People especially children walk and talk during stage III and IV.

Dream occur during REM sleep.

Brain imaging during REM sleep shows increase activity in visual area and limbic system and decreased activity in Prefrontal area reflecting dreams are related to emotional memory bank but not to thinking.


SLEEP WAKE CYCLESleep wake cycle is controlled by three neural system.1. Arousal system regulated by group of neuron in hypothalamus and involves reticular activating system (RAS) originating in brain-stem.2. Slow wave sleep center (NREM) In the hypothalamus, it has neurons that induce sleep.3. REM sleep center in the brain-stem it has neurons which become active during REM sleep 33FUNCTIONS OF SLEEPWhat is Function of Sleep?It is not clear. We spend 1/3 of our life sleeping.During Sleep brain cells are not resting, but there is change in the activity.34What is the purpose of NREM and REM sleep?Theories are 1. During metabolic activity of neuron and glial cells, Adenosine is produced from the ATP during awake state (increased adenosine when we are awake more).

Adenosine inhibits arousal center, this can bring NREM sleep (injection of adenosine induces normal sleep).

35What is the purpose of NREM and REM sleep? [cont]During sleep , Adenosine level decreases as brain uses this adenosine for replenishing its limited energy stores.

Caffeine blocks adenosine receptors in the brain, therefore causes wakefulness.

36What is the purpose of NREM and REM sleep? [cont]2. Restoration and recovery proposal During awake, brain neuron release neurotransmitter Norepinephrine and Serotonin.But during REM sleep, these neurotransmitters are not released, therefore, it restores receptor sensitivity.37What is the purpose of NREM and REM sleep? [cont]3. Sleep is necessary for learning and memory This may explain Why infants need so much sleep.38SLEEP DISORDERSInsomnia - Insomnia is difficulty in getting sleep - 10-15% of population suffer from insomnia - cause of Insomnia- may be anxiety, too much coffee, tea, soft drink, stimulants, drugs , travelling .NarcolepsyRare disorder affects 0.5% population.Person suddenly falls asleep at odd moments.May occur frequently throughout the day.

Sleep Apnea syndrome - person not breathing for a while, snoring , obesity, little sleep.


10 /20 % system of EEG electrode placement4142

EEG Machine

Sleep SpindleK - complexEEG showing sleep spindle STAGE II43

Grandmal seizure44

Petitmal seizure45USE OF EEGEEG is useful in diagnosis of 1. Epilepsy 2. Sleep Disorders 3. Brain death [used in some centers] 46POLYSOMNOGRAPHYPolysomnography is a series of tests performed on a patient with sleep disorders e.g. sleep apnea, narcolepsy

It is over night procedure and includes monitoring of ECG, blood pressure, air flow, blood oxygen level, EEG, eye movements, and movements of respiratory muscle and limbs47POLYSOMNOGRAM SLEEP STUDY48

Polysomnographic Record49