Dual routes to cortical orienting responses: novelty detection and uncertainty reduction

Sokolov distinguished between reactive and proactive variants of the orienting response (OR). The Novelty P3 is considered as an electrophysiological signature of the reactive OR. Recent work suggests that the proactive OR is reflected in frontally distributed P3 activity elicited by uncertainty-reducing stimuli in task-switching paradigms. Here, we directly compare the electrophysiological signatures of reactive and proactive ORs. Participants completed a novelty oddball task and a task-switching procedure while the electroencephalogram was measured. Novel and uncertainty-reducing stimuli evoked prominent fronto-centrally distributed Novelty P3 and Uncertainty P3 waves, respectively. We found a substantial negative correlation between Novelty P3 and Uncertainty P3 across participants, suggesting that reactive and proactive ORs converge on a common neural pathway, but also that distinguishable routes to orienting exist. Moreover, response accuracy was associated with reduced Novelty-P3 and enhanced Uncertainty-P3 amplitudes. The relation between Novelty P3 and Uncertainty P3 might serve as an index of individual differences in distractibility and cognitive control.