Effects of the amount of stimulus information processed on negative event-related potentials

Event-related potentials were recorded during simple reaction time and 3 discrimination conditions which varied in the amount of stimulus information that needed to be processed. It was found that NA became longer in duration as the amount of stimulus information that required processing was increased. Using sequential topographic mapping, it was concluded that there are at least 3 overlapping deflections that comprise NA. The experimental effect appeared to be mainly on the third deflection of NA. The problem of overlap between NA and later positive-going components, P380 and P3b, is discussed in terms of their relative latencies and scalp distributions.