Distinguishing between what is novel and what has already been experienced (or between degrees of novelty) is a fundamental process that enables one to appropriately react to stimuli in the environment. During the developmental years, when much new information is acquired, a mechanism that can quickly differentiate between the novel and the familiar is essential. Based on previous event-related brain potential (ERP) work, several different stages can be identified in the processing of novel stimuli as they become more familiar through repetition. First, when an unexpected stimulus is experienced, orienting occurs. Then, as the event becomes less novel through repetition, the orienting response habituates, indicating that some kind of memory trace has been formed. This memory trace allows the habituated event to be distinguished from other new events. In addition, future encounters with this, no longer novel, item will be facilitated. Orienting, habituation and memory processes have been measured physiologically and have been demonstrated to modulate brain activity. In order to investigate developmental trends in these processes, ERPs will be recorded from young children (ages 5-7), pre-adolescents (ages 10-12) and young adults (ages 20-25). One goal of the proposed research is to extend the findings from the auditory to the visual modality. Hence, visual novel events will be used in a visual novelty oddball task. Determining effects of stimulus familiarity on orienting and memory is another goal of the proposal that will be achieved by repeating two classes of novel stimuli, familiar and unfamiliar. Finally, an old/new recognition memory task will be employed to assess, behaviorally and physiologically, subjects' memory for novel visual events. ERPs will be recorded from 62 scalp sites to enable scalp distribution and current source density analyses, in order to determine whether orienting and memory processes and, by implication, their intracranial generators show age-related changes.
