Encephalography is the examination of the brain by radiography after the withdrawal of cerebrospinal fluid (by lumbar or cisternal puncture) and introduction of air, another gas, or contrast material.
Electroencephalography uses electrodes placed on the scalp to detect and measure patterns of electrical activity emanating from the brain. In recent years, EEG has undergone technological advances that have increased its ability to read brain activity data from the entire head simultaneously. EEG can determine the relative strengths and positions of electrical activity in different brain regions. By tracking changes in this activity during such drug abuse-related phenomena as euphoria and craving, scientists can determine brain areas and patterns of activity that mark these phenomena. The greatest advantage of EEG is speed-it can record complex patterns of neural activity occurring within fractions of a second after a stimulus has been administered. The biggest drawback to EEG is that it provides less spatial resolution than fMRI and PET do. As a result, researchers often combine EEG images of brain electrical activity with MRI scans to better pinpoint the location of the activity within the brain.