The functional neuroanatomy of novelty processing: integrating ERP and fMRI results.

Recent research indicates that non-tonal novel events, deviating from an ongoing auditory environment, elicit a positive event-related potential (ERP), the novel P3. Although a variety of studies examined the neural network engaged in novelty detection, there is no complete picture of the underlying brain mechanisms. This experiment investigated these neural mechanisms by combining ERP and functional magnetic resonance imaging (fMRI). Hemodynamic and electrophysiological responses were measured in the same subjects using the same experimental design. The ERP analysis revealed a novel P3, while the fMRI responses showed bilateral foci in the middle part of the superior temporal gyrus. When subjects attended to the novel stimuli only identifiable novel sounds evoked a N4-like negativity. Subjects showing a strong N4-effect had additional fMRI activation in right prefrontal cortex (rPFC) as compared to subjects with a weak N4-effect. This pattern of results suggests that novelty processing not only includes the registration of deviancy but may also lead to a fast access and retrieval of related semantic concepts. The fMRI activation pattern suggests that the superior temporal gyrus is involved in novelty detection, whereas accessing and retrieving semantic concepts related to novel sounds additionally engages the rPFC.