DC Potentials of the Brain

Abstract

This volume is devoted to the origin and significance of slow brain potentials beyond the frequency range of the conventional EEG. The occurrence of such ultraslow fluctuations up to sustained shifts of the baseline was well known in the early days of electroencephalography, when coil and string galvanometers served as recording instruments (cf. Brazier, 1963; O’Leary and Goldring, 1964; Gumnit, 1974a). It soon became evident, however, that leads of the slow components of bioelectrical activity were often distorted by artifacts caused, for example, by movements of head and eyes or by changes of electrode potentials. Therefore, the introduction of voltage amplifiers and high-pass filters that eliminate slow potential fluctuations and thus stabilize the baseline was generally appreciated. As a result, study of slow potentials was generally neglected for a rather long time, and it was only during the last few decades that considerable improvements in recording techniques stimulated a renewed interest in this field of research. Meanwhile, numerous investigations both on animals and in man have already shown that recordings of slow potentials provide, for instance, an objective access to the understanding of higher brain functions including such complex phenomena as cognitive processes. Studies presented in this volume can be expected to contribute further insights into such mechanisms.