Electroencephalography (EEG) is a non-invasive medical monitoring technique, used to record the brain’s electrical activities. The recording procedure involves an array of electrodes placed over a person’s scalp, a connected signal amplifier, and a personal computer to record and store the information. It can be recorded while a subject is at rest or under certain types of sensory stimulus challenges, such as light flashes, auditory tones, or somatic stimuli. It can also be recorded in combination with other neural imaging techniques, such as MRI or PET scans. The recorded data can be displayed on a monitor in real time or analyzed further offline.

EEG measures voltage fluctuations resulting from average electrical activities of massive numbers of neurons under the electrodes. In the healthy human population, brain signals are relatively consistent and normally distributed. However, pathological brain conditions often result in significant signal deviation from the norm. Some of the features have been used for clinical diagnoses for approximately a hundred years, such as spike waves for epilepsy and flat line for brain death. Other complex signals are under research for their roles in neural and cognitive functions.

A routine clinical EEG recording typically lasts about an hour including 30-40 minute preparation time. An electrode cap will be placed over the subject’s head. Each electrode on the cap will be injected with small amount of electrode gel and followed by a gentle scratch of the skin beneath with a dull needle to ensure good conductance. The subject will then be asked to relax with their eyes closed during the entire recording. Occasionally, they will be asked to perform certain actions such as hyperventilating, or be given light stimulation to check for potential epilepsy.

*Please be notified that the EEG study used by BHLF is not a substitute for clinical decisions. It can only be used by professionals to help make or rule out the following diagnoses:

• Epilepsy or other seizure disorders

• Brain injury

• Stroke

• Brain degenerative disorders

• Sleep disorders

• Mental disorders

• Substance use disorders