Another exam performed in the sleep diagnostic center is an electroencephalogram (EEG.)  An EEG is a test which detects abnormalities associated with electrical activity of the brain.  Small electrodes are placed on the scalp and the signals are recorded on a computer.  Doctors can use this test to look for abnormal patterns which might cause sleep problems, seizures (physical findings or changes in behavior that occur after an episode of abnormal electrical activity in the brain), or other neurological problems.  Sometimes this test is ordered to be done while a patient is sleeping; other times it is ordered to be done on a patient during wakeful hours.