On the functional significance of Novelty-P3: facilitation by unexpected novel sounds.

The unexpected occurrence of a change in the auditory context has been shown to result in distraction due to a momentary attention shift. These unexpected sounds elicit the Novelty-P3 (NP3) response which has been proposed as an electrophysiological index of distractibility, and used as such in the evaluation of several clinical populations. However, unexpected sounds also result in facilitation under certain conditions. Here, we investigate the electrophysiological concomitants of novel sounds in a task in which these sounds facilitate visual task performance. Novel sounds elicited NP3 and resulted in an enhancement of the visual P300 response to subsequent visual targets. This result clearly argues against the use of NP3 as an index of distractibility and asks for a reformulation of the functional significance of this response. We suggest that the NP3 is a complex signal that comprises alerting, orienting and executive control processes triggered by the unexpected stimulus.