LARRY MULVEHILL / SCIENCE PHOTO LIBRARY. LARRY MULVEHILL / SCIENCE PHOTO LIBRARY.
Young boy undergoing an Electroencephalograph (EEG) examination in a U.S. hospital, showing the EEG technician attaching numerous electrodes to his head. The EEG records the electrical activity of the brain's surface via the scalp through the differences in readings from the numerous electrodes. Sixteen electrodes are typically used. The results are printed out onto a moving strip of paper, and appear as characteristic waveforms, some of which may be indicative of disease (epilepsy and dementia), drug disturbances or states of anxiety. An example of a normal "brainwave" pattern is the alpha wave, observed in healthy adults during sleep.
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