Stimulus parameter effects on the P50 evoked response

Abstract

Recently, there has been a surge in interest in studying the midlatency auditory evoked responses (MLAERs) in psychiatric populations. The P50 component of the MLAERs received special attention, as it was shown not to be affected by attentional factors (Jerger et al 1992). An inherent limitation of recording the MLAERs is their tendency to decrease in amplitude with fast rates of repetition. Buchwald et al (1991) showed that the P50 amplitude decreases when the stimuli were presented at rates of 5 and 10/sec as compared with l/sec. They did not study the effects of slower rates of stimulation. This decreased amplitude has been postulated to be secondary to a slow recovery cycle of the neuronal aggregates subserving the P50 response (Eccles 1969). To avoid this confounding factor, researchers need a standard 10-sec interval between stimuli, to assure full neuronal recovery prior to repeating stimulation (Barker et al 1987; Boutros et al !991a). As is customary in evoked potential research, many responses need to be averaged together. The required number of single trials needed to produce a good tracing varied between 30 trials (Nagamoto et al 1989), requiring only 5 min of recording, to up to 120 trials (Boutros et al 1991b), requiring 20 min