[The objective and perspective of recording electrical activity from the central nervous system]

In 1929 Hans Bergr successfully recorded electrical activity from the human brain using surface scalp electrodes. Since, the EEG has brought significant contributions to the fields of clinical neurology and neurophysiology. As a clinical diagnostic tool, the EEG has provided information for functional as well anatomical (structural) brain disturbances. As a functional diagnosis, the EEG is far superior to other functional tests such as PET, SPECT or functional MRI because of its excellent temporal resolution representing moment to moment changes in the level of consciousness. However, the progress has been hampered due to difficulty in quantifying EEG data because of its extreme dynamics and variability, which perhaps reflects yet unknown brain functions. This difficulty will be overcome by improved quantification methods and statistical measures using various computer applications including topographic mapping, power spectrum analysis, covariance, correlation or coherence function. Because of its poor spacial resolution, the EEG has relinquished its place to CT and MRI scans as an anatomical diagnostic tool. The surface recorded electrical activity is greatly attenuated and distorted by the time it reaches to the scalp. This is due to the inhomogeneous tissues (CSF, dura, skull, scalp) that intervene between the recording electrodes and cortical surface. Because the human body or head consists of electroconductive media of various geometries, current distortion, far-field potentials or paradoxical lateralizations further complicate the interpretation of EEG in postulating the location of anatomical generator sources from surface recorded EEG. Advanced computer technology is in progress to quantify the EEG data by taking into account the factors of conductivity, geometry shape and individual head size. This will improve the accuracy of localizing current generator sources in relationship to brain anatomy. By solving these problems in a methodical fashion, EEG will become the revelation for understanding the functional anatomy of brain and will step closer to Berger's dream, "EEG is a window of human mental activity".