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EEG measures electrical activity in the brain via electrodes on the scalp. The signals are amplified and recorded as brainwaves, which can be grouped into different frequencies. EEGs are used to record brain activity during different behaviors and to measure epileptic activity.
Electroencephalography (EEG) is the measurement of electrical activity in the brain. The measurement and graphical representation are recorded via electrodes placed on the scalp. Electrical activity in the brain passes through electrodes, which are connected to an EEG amplifier. The signals within the brain are of low amplitude, so an EEG amplifier is used to ‘amplify’ brain activity and make it more visible. Brain activity is then recorded via an EEG amplifier and graphed as waves also known as brainwaves.
When neurons or nerve cells fire simultaneously throughout the brain, the action potentials produced cause a significant change in electrical charge that is large enough to be registered by the electrodes. These electrodes are conductors that are placed along the surface of a thoroughly cleansed scalp. They allow electrical activity to pass through them, and by placing numerous electrodes on the scalp, electrical activity within different areas of the brain can be recorded simultaneously. The electrodes are connected via a cable to an EEG amplifier, such as a polygraph, and it is this machine that records the physiological changes that occur within different areas of the brain.
An EEG recording can be monopolar or bipolar. A unipolar recording occurs when a single electrode measures brain activity against an indifferent, distant electrode, while a bipolar recording measures brain activity between a pair of electrodes. The measurement takes place in the form of waves and consists of different frequencies. These frequencies are grouped as falling within the range of alpha (8-13 hertz), beta (13-30 hertz), delta (0.5-2 hertz), or theta (4-7 hertz). An EEG amplifier allows brain waves to be recorded, often resulting in particular waveforms that are characteristic of certain behaviors; for example, when an individual is relaxed, alpha activity is usually recorded.
EEGs have been implemented to record brain activity during different behaviors. They have been used to record brain activity during sleep and have also been used to measure epileptic activity such as seizures. Epilepsy is a condition characterized by recurrent partial or generalized seizures. Partial seizures occur in one hemisphere of the brain from a specific area, while generalized seizures start in various areas and result in a loss of consciousness. EEG recordings help distinguish whether a seizure is partial or generalized by measuring the significant change in brain activity that occurs during epileptic activity.
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