Event-related brain potentials in normal children during detection of inverse serial digits

Three inverse serial digit detection tasks were evaluated with event-related brain potentials (ERPs) in 15 11-year-old children to determine how the increase of perceptual or memory demands could modify detection processing. Reaction times were significantly longer for the task that used visual blurring, compared to that with a greater memory demand. Difference-ERPs (target minus non-target conditions) showed three significant parietal components; one earlier positive peak at 162 ms interpreted as an index of working memory load; a same polarity 295 ms peak which probably represents a P3 analogous and a subsequent negative polarity component (520 ms) possibly involved with motor preparation. A fourth difference-component was a frontal positive peak at 680 ms, interpreted as related to task difficulty.