EEG

EEG (Electro-Encephalography) : is a method used to record variations in electrical activity in the cortex of the brain.
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Electroencephalograph or EEG
A machine that records electromagnetic activity in the brain (the so-called "brain waves"), usually upon a moving roll of paper.
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and the plethysmograph, which measures the changes in blood volume in the finger that are caused by the dilation and constriction of blood vessels. Less often use is the electroencephalograph (EEG), which measures brain activity.

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