100 years of electroencephalography (EEG) in human medicine

Sub: Science and tech

Sec: Health

Context:

Electroencephalography(EEG) has completed 100 years of its discovery and still remains a crucial tool for understanding the brain.

What is EEG?

EEG stands for electroencephalography.
It is a test performed to detect abnormalities in your brain waves, or in the electrical activity of your brain.
Neurons in the brain perform various functions by moving electrically charged particles such as ions.
The movement of these particles gives rise to electrical activity that a health worker can use an EEG test to visualize.

How does an EEG test work?

During an EEG, electrodes are pasted onto the scalp of the patient.
These are small metal disks with thin wires and detect tiny electrical charges that result from the activity of brain cells.
These charges are amplified and appear as a graph on a computer screen or as a recording that may be printed out on paper.
Health workers are typically interested in two types of data in the graph:
- The voltage (measured in millionths of a volt).
- The frequency of the variations (measured in hertz).
The EEG procedure is usually carried out by a highly trained specialist, called a clinical neurophysiologist.
Volume conduction refers to the movement of electrical activity through this three-dimensional volume. It also stands for the fact that the electrical activity is produced in one place whereas the detectors that detect it are located at some distance.
EEG is better than other diagnostic devices at tracking relatively rapid electrical activity in the brain, in the order of milliseconds.

What is the significance of EEG?

An EEG can be used to help diagnose and monitor a number of conditions affecting the brain.
The main use of an EEG is to detect and investigate epilepsy, a condition that causes repeated seizures.
In research, scientists use EEG for neuroscience, cognitive psychology, neurolinguistics, and neuromarketing studies and to develop brain-computer interfaces.
An EEG might also be helpful for diagnosing or treating the following disorders:
Brain tumor
Brain damage from head injury
Brain dysfunction that can have a variety of causes (encephalopathy)
Inflammation of the brain (encephalitis)
Stroke
Sleep disorders

Shortcomings of EEG:

EEG is biased towards electrical signals generated closer to the surface of the cortex, and significantly so towards currents generated by neurons’ dendrites and against those generated by the axons.
To overcome these and other challenges, researchers have used EEG together with other tests, like magnetic resonance imaging (MRI), and have developed sophisticated data acquisition, processing, and reconstruction methods.