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 "od dball" paradigms. Whether detection of a sensory oddball reflects the opera tion of a generic mechanism or, alternatively, mechanisms sensitive to spec ific attributes of stimulus deviance is unknown. To address this question w e used event-related functional MRI (fMRI) to measure neural responses duri ng presentation of nouns, of which a proportion were perceptually, semantic ally, or emotionally deviant. Oddballs, regardless of deviant attributes an d depth of processing, activated right inferior pre frontal and bilateral p osterior fusiform cortices. Attribute-specific responses, independent of de pth of processing, were evident in bilateral fusiform cortices for perceptu al oddballs and left amygdala for emotional oddballs. By contrast, an inter action with depth of processing was evident in left prefrontal cortex for s emantic oddballs. We conclude that detection of oddballs reflects the opera tion of a generic "deviance detection system," involving right prefrontal a nd fusiform cortices in addition to specific brain regions sensitive to the stimulus attributes that determine the qualitative characteristics of devi ance. (C) 2000 Academic Press.