Evaluation of Event-related Slow Potentials in Selected Groups of Psychiatric Patients

Abstract

This chapter describes an experiment for the evaluation of event-related slow potentials in selected groups of psychiatric patients. Contamination of the Contingent Negative Variation (CNV) by potentials emanating from other sources, that is, electrical fields of the eye sand the skin, presents methodological problems that increase when psychiatric populations are studied. Because the level of ambient light is an important factor in determining the amplitude of the electrooculogram, which is larger in high levels of illumination, recordings were made with the patients in a comfortable darkened environment. To minimize the involvement of eye potential contamination, only auditory warning and imperative stimuli were used. Eye potentials were monitored by placing two electrodes diagonally across the eye. Using a tangent screen and perimeter, eye movements were calibrated periodically for size and direction and the appropriate sensitivities set.