Brain mechanisms for detecting perceptual, semantic, and emotional deviance.

The observation that we note the exceptional over the mundane has been the subject of extensive psychological and electrophysiological analysis in "oddball" paradigms. Whether detection of a sensory oddball reflects the operation of a generic mechanism or, alternatively, mechanisms sensitive to specific attributes of stimulus deviance is unknown. To address this question we used event-related functional MRI (fMRI) to measure neural responses during presentation of nouns, of which a proportion were perceptually, semantically, or emotionally deviant. Oddballs, regardless of deviant attributes and depth of processing, activated right inferior prefrontal and bilateral posterior fusiform cortices. Attribute-specific responses, independent of depth of processing, were evident in bilateral fusiform cortices for perceptual oddballs and left amygdala for emotional oddballs. By contrast, an interaction with depth of processing was evident in left prefrontal cortex for semantic oddballs. We conclude that detection of oddballs reflects the operation of a generic "deviance detection system," involving right prefrontal and fusiform cortices in addition to specific brain regions sensitive to the stimulus attributes that determine the qualitative characteristics of deviance.