The positrons combine with negatively charged electrons normally found in the body's cells to produce gamma rays. The PET device detects the gamma rays and converts them into color-coded images. PET is used to diagnose epilepsy and tumors and help in planning neurosurgery. In brain mapping, PET gives a working portrayal of many brain functions. EEG EEG, or electroencephalography, records the brain's electrical activity.
Brain cells produce electricity when they are active.
Electrodes placed on a person's scalp record the voltage. An EEG session can help diagnose epilepsy, stroke or head injury. In brain mapping, it is most valuable in identifying how long it takes the brain to perform functions. EEG devices record in intervals of 1 millisecond, the equivalent of 1,000th of a second. The EEG also detects voltage fluctuations common in cognitive exercises and approximate locations of the activity.