A German doctor in 1929 named Hans Berger - considered the Father of EEG - announced his discovery that it was possible to record the electrical impulses of the brain and display them graphically on paper. He discovered that these electrical impulses changed according to the brain's activity, whether in sleep, under sedation, with lack of oxygen, and in certain nerve disorders like epilepsy. Berger laid the groundwork in the field that today is known as clinical neurophysiology.
EEG represents the activity of a certain area of the brain. The EEG pattern in the during recording can change under normal circumstances, not only where disease in indicated. An experienced specialist is required to decipher or interpret the results from an EEG. EEG traces change if brain activity changes. The sleep EEG recording or traces look different from that of awake. The traces can shows when in a light or deep stage of sleep. Normal brain activity is distinguished from abnormal function.