Answer
Electroencephalography (EEG) is a technique used to measure electrical activity in the brain--mainly the cerebral cortex. The record produced is called an electroencephalogram The EEG device ( electrodes, amplifier, filter and recording unit) is used to monitor and display the electrical activity of the brain --brain waves.
There are four kinds of brain wanes -- alpha waves, beta waves, theta waves, and delta waves. These waves have characteristic ranges in frequency and voltage. Within these ranges, each type of wave exhibits temporal rhythmic changes that together present pictures representative of differences in physiological activities of the brain. These differences are known to be indicative of normal functioning or abnormal states of consciousness--alertness, sleep, coma. Pathological conditions such as degenerative brain diseases ,and metabolic abnormalities(Tay-Sachs, Sialidosis, Menkes disease), as well as brain injury due to physical trauma. show diagnostic EEG wave patterns.
Work Step by Step
There are four types of brain waves monitored by EEG technology. These are alpha waves, beta waves, theta waves, and delta waves; They vary in frequency and amplitude, and predominate in certain physiologic and pathologic situations:
Alpha waves have a frequency range of 8-13 Hz, and an amplitude range of 50-100 uV;
They predominate in the EEG when the subject is awake and resting with eyes closed and mind
wandering
Beta waves have a frequency (fq) of 13-40 Hz and a voltage of >20 uV . These waves dominate the EEG
during mental activity, and sensory stimulation.
Theta waves dominance in the awake adults indicates either emotional stress or a brain disorder. These
waves have a fq range o 4-7 Hz voltages that are usually greater than 50 uV.
Delta waves are high amplitude (>50uV) , slow waves--heir frequency is usually lower than 4Hz, A
predominance of these waves in awake adults is usually an indication of serious brain damage.
EEE technology has very important clinical and legal importance.. In normal healthcare facilities, EEG is used to monitor consciousness/alertness as well as stages and quality of sleep .
It is also used to detect abnormal brain functioning caused by physical brain trauma,, metabolic malfunctioning or by degenerative brain disease.
Coma and legal clinical death in hospitals are usually diagnosed and confirmed by electroencephalography. Coma is usually described as a state of of unconsciousness in which eyes are closed, breathing is irregular and the patient is unresponsive to light and painful stimuli. The EEG pattern is usually flat in this case, but there may still be electrical activity below the cortex --in the hypothalamus.
The well-known flat line EEG in which the characteristic rhythmical changes in EEG wave amplitudes are lost is usually accepted as an indication of clinical death. However, for legal purposes this is not enough. In forensic medical situations, it is usually necessary to carry out confirmatory tests,--such as apnea tests, and a complete neurological test-- before pronouncing a patient dead
