A thorough understanding of Electroencephalography

Hyderabad: This article is in continuation of the previous articles that help you understand what constitutes the biological sciences and its varied branches/ concepts. Today, we would be discussing the third part of the Biomedical technology with a focus on Electroencephalography (EEG).

Electroencephalography (EEG)

• Electroencephalography is the process of recording the electrical activity of the brain (graphical recording called electroencephalogram) with the help of an EEG machine and some electrodes placed all over the scalp.
• Electroencephalograph is a useful tool in diagnosing neurological and sleeping disorders.
• The changed EEG patterns in the case of epilepsy are conveniently studied with the help of an EEG.
• Brain shows continuous electrical activity of innumerable neurons.
• The intensity and pattern of electrical activity depends on wakefulness, sleep, coma, and certain pathological and psychological conditions.
• The main diagnostic application of EEG in neurological studies is the diagnosis of epilepsy (seizures).
• EEG shows distinct abnormal pattern in the case of epilepsy.
• EEG is also useful in the diagnosis of coma and brain death.
• EEG studies are useful in analyzing sleep disorders (such as insomnia).

Waves of EEG

• The waves recorded by an EEG consist of

a. Synchronized waves which are common in normal healthy people

b. In certain neurological conditions, the waves are desynchronised (irregular wave pattern).

• The wave pattern can be broadly classified into Alpha, Beta, Theta & Delta waves patterns.
• The nature of the waves depends on the intensity of activity of the different part of the cerebral cortex.

Alpha waves

• They are rhythmical 8-13 cycles per second.
• This type of wave pattern is seen in persons who are drowsy/sleepy with closed eyes.

Beta waves

• These waves occur at a high frequency of 13-40 cycles per second.
• Their amplitude is low.
• These are desynchronised waves recorded in persons who are mentally very active and tense.

Delta waves

• Their frequency is quite low (less than 3 cycles per sec).
• However, they have high amplitude.
• They are common in early childhood in awaken condition.
• In adults they occur in deep sleep.
• In the case of brain tumors, epilepsy, mental depression etc.
•  These waves occur in awake adults too.

Theta waves

• Their frequency is between 4 and 7 cycles per second.
• These waves are common in children of less than 5 years of age.
• They are also recorded during emotional stress in adults.

ECG

• The word ECG means Electrocardiogram/ Electrocardiograph, but it is most commonly used for electrocardiogram.
• Electrocardiograph is commonly used as non-invasive procedure for recording electrical changes in the heart.
• The graphic record, which is called an electrocardiogram (ECG/EKG), shows a series of waves that relate to the electrical impulses which occur during each cardiac cycle.
• An electrocardiograph is a device which records the electrical activity of the heart muscle (de-polarisations and repolarisations).

What is electrocardiography?

• Electrocardiography is the technique by which the electrical activities of the heart are recorded for study.
• Sensors (electrodes) are placed at specific parts of the body and linked to the ECG machine.
• ECG is recorded using 12 leads (sensors from limbs and chest)
• Obtaining an electrocardiogram typically take a few minutes, after which the electrodes are removed.