Isolation of faster components in the electroretinogram and visually evoked response in man.

The electroretinogram (ERG) response evoked in man by intense illumination pre­ sents a series of oscillatory potentials super­ imposed on the b-wave." These oscillatory potentials are of clinical importance, since in the presence of certain diseases they are reduced or disappear prior to some changes of the aand b-waves. Measurement of the amplitude of the os­ cillatory potential is difficult, since the con­ figuration of the oscillatory potential is af­ fected by the inclination of the b-wave. To delineate the oscillatory potential clearly, short amplifier time constant recording (for example, 0.01 second) has been recom­ mended. In this range of amplifier time con­ stant, the aand b-waves are still too large to isolate the ocillatory potentials. It was demonstrated that rhythmic wave­ lets are superimposed on the human visually evoked response (VER) produced by in­ tense illumination.' These VER wavelets are small and much distorted by slow compo­ nents, making clear identification difficult. The purpose of the investigation reported here was to isolate the oscillatory potentials and VER wavelets by eliminating the slow components of the ERG and VER with band pass filters.