On the functional role of temporal and frontal cortex activation in passive detection of auditory deviance.

The superior temporal cortex (STC) and inferior frontal cortex (IFC) are active during pre-attentive change detection. According to one influential model, the temporal cortex is responsible for memory trace comparison and the frontal cortex for attention switching. However, fMRI studies that used parametric designs revealed frontal cortex activity that is inconsistent with this model. In response, alternative accounts of frontal cortex activity, such as contrast enhancement and response inhibition, have been suggested. In this study, we measured the event related potential (ERP) and event related optical signal (EROS) responses elicited by pitch deviants in a parametric design. The ERP results revealed the typical modulation of mismatch negativity (MMN) amplitude by degree of deviance. The EROS results showed a similar modulation effect in the temporal cortex and a general temporal cortex followed by frontal cortex activation pattern. Interestingly, medium deviants elicited a greater frontal EROS response than did large or small deviants. Moreover, regression analyses showed that the EROS measures, specifically the linear trend in the temporal cortex and the inverse quadratic trend in the frontal cortex, correlated with the linear trend of the ERP MMN response. Taken together, these results indicate that 1) deviance magnitude modulates the brain activity elicited by pitch stimuli in the STC and IFC within the same time range as electrophysiological measures of passive deviance detection, 2) EROS measures of deviance detection are highly correlated with the ERP MMN, and 3) the functional relationship of STC and IFC is consistent with both the contrast enhancement and response inhibition accounts of IFC activity in passive deviance detection.