Dr.M.Arivumani

EEG 1

EEG2

EEG 3

EEG 4

EEG 5

Function of EEGThe EEG uses highly conductive silver electrodes coated

with silver-chloride and gold cup electrodes to obtain accurate measures… use impedance device to measure effectiveness, resistance caused by dura mater, cerebrospinal fluid, and skull bone

Monopolar Technique : the use of one active recording electrode placed on area of interest, a reference electrode in an inactive area, and a ground

Bipolar Technique : the use of two active electrodes on areas of interest

Measures brain waves (graphs voltage over time) through electrodes by using the summation of many action potentials sent by neurons in brain. Measured amplitudes are lessened with electrodes on surface of skin compared to electrocorticogram

Sodium-Potassium PumpThe mechanism within neurons that creates action

potentials through the exchange between sodium and potassium ions in and out of the cell

Adenosine Triphosphate (ATP) provides energy for proteins to pump 300 sodium ions per second out of the cell while simultaneously pumping 200 potassium ions per second into the cell (concentration gradient)

Thus making the outside of the cell more positively charged and the neuron negatively charged

This rapid ionic movement causes the release of action potentials

HistoryRichard Caton (1875) –localization of sensory functions with

monkeys and rabbitsHans Berger (1924) – first EEG recording done on humans

- described alpha wave rhythm and its suppression compared to beta waves

- acknowledged “alpha blockade” when subject opens eyes

William Grey Walter – influenced by Pavlov and Berger, further developed EEG to discover delta waves during sleep (1937) and theta waves (1953)

Alpha WaveCharacteristics:

- frequency: 8-13 Hz-amplitude: 20-60 µV

Easily produced when quietly sitting in relaxed position with eyes closed (few people have trouble producing alpha waves)

Alpha blockade occurs with mental activity -exceptions found by Shaw(1996) in the case of mental arithmetic, archery, and golf putting

Alpha

Beta WavesCharacteristics:

-frequency: 14-30 Hz-amplitude: 2-20 µV

The most common form of brain waves. Are present during mental thought and activity

Beta

Theta WavesCharacteristics:

-frequency: 4-7Hz-amplitude: 20-100µV

Believed to be more common in children than adultsWalter Study (1952) found these waves to be related to

displeasure, pleasure, and drowsiness Maulsby (1971) found theta waves with amplitudes of

100µV in babies feeding

Delta WavesCharacteristics:

-frequency: .5-3.5 Hz-amplitude: 20-200µV

Found during periods of deep sleep in most peopleCharacterized by very irregular and slow wave patterns Also useful in detecting tumors and abnormal brain

behaviors

Gamma WavesCharacteristics:

-frequency: 36-44Hz-amplitude: 3-5µV

Occur with sudden sensory stimuli

Less Common WavesKappa Waves:

-frequency: 10Hz-occurred in 30% of subjects while thinking in Kennedy et al.(1948)

Lambda Waves:-amplitude: 20-50µV-last 250 msec, related to response of shifting visual image-triangular in shape

Mu Waves:-frequency: 8-13Hz-sharp peeks with rounded negative portions (7% of population)

Sleep and The EEG

Sleep and EEG cont’d: Different stages of sleep and their respective brain waves:

Stage 1: Low voltage random EEG activity (2-7 Hz) Stage 2: Irregular EEG pattern/negative-positive spikes (12- to 14- Hz)

Also characterized with sleep spindle and K-complexes that could occur every few seconds.

Stage 3: Alternative fast activity, low/high voltage waves and high amplitude delta waves or slow waves (2 Hz or less).

Stage 4: Delta waves Stage REM (Rapid eye Movement): “episodic rapid eye movements,” low

v voltage activity. Stage NREM: All stage combined, but not including REM or stages that

may contain REM.

The K-complex occurs randomly in stage 2 and stage 3 The K complex is like an awaken state of mind in that is associated with

a response to a stimulus that one would experience while awake.

EEG brain waves in the Sleep Cycle:

Position of electrodes

A1-lefrt ear A2-right earFp-frontal pole leadsF-frontal leadsP-parietal leadsC-central leadsT-temporal leadsO-occipital leads

Spikes and slow wave copmlexes- typical- 3/sec-absence seizures fast - 4-6/sec-myoclonic jerks slow -1-2.5/sec-intractable epilepsy with MR

Polyspikes –these rapid Polyspikes are found in GTCS Post traumatic epilepsy Lennox gastaut syndrome

INDICATIONEpilepsy-diagnosis,classify,monitoring

response to treatment,predicting prognosisComatose and confused patientsNon neurological disorderDegenerative diseasePsychological and behavioural problems

EEG 1

Fast Spike and wavecomplexes

GTCS

EEG 2

Repitive Spike on left side-right sidedpartial seizure

EEG 3

Spike and slow

wave complex3/sec

absence seizure

EEG 4

High voltage delta activity-deeply comatose patient

EEG 6

SSPE-Periodic discharges at 4 sec interval. Maximum at fronto central areas Giant slow waves mixed with several sharp waves

REFERENCES CLINICAL ENCEPHALOGRAPHY-U K

MISRA J

KALTIA

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