Printed in U.S.A. Modification of the EEG Time Constant by Digital Filtering

A method is proposed for modifying the time constant of an EEG amplifier after the recording. It is based on digital filtering and works for single sweeps, averaged potentials, and other neurophysiological data, e.g. spontaneous EEG. The validation is based on calibration signals and data from a study on event-related potentials. DESCRIPTORS: Time constant. Slow potentials, Digital filtering. We present here a computer algorithm for the modification of the time constant of an EEG amplifier to any desired vaiue. This possibility is of interest in particular for researeh on slow potentials and to a somewhat lesser degree for the sponta-neous EEG: as has been pointed out by Duncan-Johnson and Donchin (1979), there is a great varia-bility in the time constant used which may lead to spurious differences between studies. Further