When you think about the fact that the brain and nervous system are like electrical wiring in the body, it's easy to understand that electrical impulses can be measured, and therefore, studied.
Neurophysiology includes all the electrical tests that study the function of the brain and nerves.
Each kind of test is ordered by your physician for specific purposes. EEGs are often done during surgery on the arteries of the neck to make sure there is enough blood flow to the brain. During an EEG, small pads are placed on the head to record brain waves. EEG cannot record thought, and the test is totally painless. EPs are used to diagnose disorders of the nervous system such as Multiple Sclerosis hearing loss spinal cord problems.