Electroencephalogram [EEG]
Electroencephalogram [EEG]
Electroencephalography (EEG) is the measurement of the neuronal activity of the brain. The resulting traces are called electroencephalogram. Cells of the brain communicate with the help of tiny electrical impulses. By placing electrodes on the scalp, it is possible to record these electrical impulses and analyze the activity of the brain.
The electrical activity of the brain has been under study ever since 1875, when Richard Caton published his findings about electrical activity in cerebral hemispheres of rabbits and monkeys. Hans Berger, a German physiologist, is sometimes credited with the invention of EEG. He started research on human EEG in 1920 and gave the device its name. Berger’s work was expanded later on by Edgar Adrian Douglas.
Electroencephalography can detect many diseases of the brain like epilepsy, brain tumors, infections like encephalitis, head injury, diseases like Parkinson’s disease and various sleep disorders. EEG is also used to monitor the brain’s activity during surgical procedures and to confirm clinical death.
There are four types of brain waves: Alpha (8 to 12 Hz), Beta (13 to 30 Hz), Delta (less than 3 Hz) and Theta (4 to 7 Hz). Alpha waves are present in waking state when eyes closed. Beta waves are present when the person is fully awake. Delta waves are found during sleep and in young children. Theta waves are normally found only in children or during sleep.
An electroencephalogram is usually done in a hospital by an EEG technologist. During the test, 16 to 25 electrodes are placed on the head using a sticky paste. Sometimes a cap with fixed electrodes may be used instead of individual electrodes. These electrodes are connected to a machine that amplifies and records the electrical activity of the brain. The electrical activity may be traced on a moving piece of paper or on a computer monitor.
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- Computed tomography [CT Imaging]
- Magnetic resonance imaging [MRI]
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