Predictive value of novel stimuli modifies visual event-related potentialsand behavior

Objective: We examined how behavioral context influences novelty processing by varying the degree that a novel event predicted the occurrence of a sub sequent target stimulus. Methods: Visual event-related potentials (ERPs) and reaction times (RTs) we re recorded in 3 detection experiments (23 subjects). The predictive value of a novel stimulus on the occurrence of a subsequent target was varied as was novel-target pairing intervals (200-900 ms). In Experiment 1, novel sti muli always preceded a target, in Experiment 2, 40% of novel stimuli were f ollowed by a target, and in Experiment 3, novel stimuli occurred randomly. Results: In Experiment 1, RTs following 100% predictive novels were shorten ed for targets at all spatial locations and novel-target pairing intervals. Novel stimuli predicting a target generated a central negativity peaking a t 300 ms and reduced P3a and P3b ERPs. In Experiments 2 and 3, target RTs w ere prolonged only when novel and target stimuli were presented in the same spatial location at short ISIs (200 ms). The central novel N2 was smaller in amplitude in comparison to Experiment 1, and novelty P3a and target extr astriate N2 and posterior scalp P3b ERPs were enhanced. Conclusions: The enhanced N2 for 100% predictive novel stimuli appears to i ndex an alerting system facilitating behavioral detection. The same novel s timuli with no predictive value distract attention and generate a different ERP pattern characterized by increased novelty P3a and target P3b response s. The results indicate that behavioral context determines how novel stimul i are processed and influence behavior. (C) 2000 Elsevier Science Ireland L td. All rights reserved.