The human electroencephalogram (EEG) was first described by Professor Dr. Hans Berger of Jena. It is known that all living cells, both animal and plant, can generate electrical currents, which are called bioelectric currents. These currents are different from those caused by injuries, such as demarcation, alteration, or longitudinal cross-section currents. It was expected that the central nervous system, which consists of a large number of cells, would exhibit bioelectric phenomena. This was indeed confirmed relatively early. Caton (1874) conducted experiments on the brains of rabbits and apes, using unpolarizable electrodes placed on the surfaces of both hemispheres or one on the cerebral cortex and the other on the skull. He observed distinct current fluctuations, which were particularly pronounced when the animal was awake from sleep and at death, and then gradually disappeared. Caton also noted that strong current fluctuations occurred when the eye was exposed to light, and he speculated that these cortical currents could be used for localization within the cerebral cortex. Fleischl von Marxow (1883) first observed that when two symmetric points on the surface of the cerebral hemisphere were connected with unpolarizable electrodes, only small or no deflections were recorded. However, when peripheral stimuli, such as eye illumination, were applied, clear deflections occurred, especially when the electrodes were near the optic centers. Chloroform anesthesia suppressed these deflections, but they reappeared when the animal awoke. He also demonstrated that these currents could be recorded from the exposed cerebral cortex, the dura mater, and even from the skull bone. Beck (1892) found that when two points on the cerebral cortex were connected, a continuously varying current was present, which did not correlate with breathing or heartbeat. This current disappeared during anesthesia, but reappeared when peripheral sensory organs were stimulated. These findings laid the foundation for the study of the human EEG.The human electroencephalogram (EEG) was first described by Professor Dr. Hans Berger of Jena. It is known that all living cells, both animal and plant, can generate electrical currents, which are called bioelectric currents. These currents are different from those caused by injuries, such as demarcation, alteration, or longitudinal cross-section currents. It was expected that the central nervous system, which consists of a large number of cells, would exhibit bioelectric phenomena. This was indeed confirmed relatively early. Caton (1874) conducted experiments on the brains of rabbits and apes, using unpolarizable electrodes placed on the surfaces of both hemispheres or one on the cerebral cortex and the other on the skull. He observed distinct current fluctuations, which were particularly pronounced when the animal was awake from sleep and at death, and then gradually disappeared. Caton also noted that strong current fluctuations occurred when the eye was exposed to light, and he speculated that these cortical currents could be used for localization within the cerebral cortex. Fleischl von Marxow (1883) first observed that when two symmetric points on the surface of the cerebral hemisphere were connected with unpolarizable electrodes, only small or no deflections were recorded. However, when peripheral stimuli, such as eye illumination, were applied, clear deflections occurred, especially when the electrodes were near the optic centers. Chloroform anesthesia suppressed these deflections, but they reappeared when the animal awoke. He also demonstrated that these currents could be recorded from the exposed cerebral cortex, the dura mater, and even from the skull bone. Beck (1892) found that when two points on the cerebral cortex were connected, a continuously varying current was present, which did not correlate with breathing or heartbeat. This current disappeared during anesthesia, but reappeared when peripheral sensory organs were stimulated. These findings laid the foundation for the study of the human EEG.