|MadSci Network: Neuroscience|
Mark, The simple answer to your question is yes, people in comas have brain waves. But, this does not mean that they are only 'asleep'. The measurement of brain waves (called electroencephalography or EEG) can show the activity level of the brain. When people are awake they display certain types of brain waves that are characteristic of high activity. During sleep, these same high activity brain waves can still be recorded, especially when the person is dreaming. A coma is a condition that is behaviorally and physiologically different from sleep. A person in a coma is unconscious and not able to be awakened. This differs from sleep, because you can easily wake up someone who is asleep. Coma and sleep also differ in the amount of blood that flows into the brain (blood carries oxygen and the brain needs more oxygen than any other organ in the body). During sleep, the blood flow in the brain is the same or higher than when the person is awake. However, in a coma, the blood flow is always lower. The brain waves, or EEGs, of coma patients are also different from patients who are awake or sleeping, but not all coma patients have the same EEG patterns. Doctors can often tell what part of the brain was injured and thus tell what caused a coma by looking at EEGs. Additionally, there are different levels of coma. While you cannot 'wake up' a person in a coma, some coma patients can respond to some stimuli. For example, some patient's EEGs show a reaction when a loud noise is made near the ear. Other patients in coma show absolutely no reaction to any stimuli. Once a person has no brain waves, that person is said to be 'brain dead'. Hope this answered your question.
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