What does the P300 brain response measure in children? New insight from stimulus sequence studies

THE decrease in the P300 brain response latency with increasing age is ofte n taken to reflect maturation of cognitive processes in children. We found that in abnormally distractible children the auditory P300 latency decrease d significantly when the inter-target interval (ITI) increased in a stimulu s discrimination task. We speculate that the sensory memory trace of the ta rget stimulus may decay in distractible children during longer ITIs, and co nsequently the next target stimulus may activate the brain's orienting netw orks that are known to generate shorter latency brain responses. The relati ve strength by which the functionally different neural networks underlying the cognitive brain responses are activated may contribute significantly to the latency measures of these responses. The presumption that a short P300 latency equals to fast processing may thus be over-simplistic, especially in children. (C) 1999 Lippincott Williams & Wilkins.