The functional role of the frontal cortex in pre-attentive auditory change detection

Accounts of the functional role of the frontal cortex in pre-attentive auditory change detection include attention switching, response inhibition, contrast enhancement, and activation of a predictive model. These accounts assume different sequential activation patterns between the temporal and frontal cortices: Change detection in the auditory areas of the superior temporal cortex (STC) followed by inferior frontal cortex (IFC) activation for attention switching and response inhibition; STC preceded by IFC activation for contrast enhancement; and an IFC-STC-IFC activation sequence for the predictive model. We used the event-related optical signal (EROS), which provides a temporal resolution of milliseconds and a spatial resolution of 5 to 10 mm, combined with lagged correlation path modeling to examine the response of the right frontal and temporal cortices to auditory duration deviants of varying magnitude. Event-related potentials (ERPs) were also recorded, as was the slow optical (hemodynamic) brain response. The data analyses revealed temporal-frontal, frontal-temporal-frontal, and temporal-frontal activation patterns when the deviants represented relatively large, medium, and small changes from the standard stimulus, respectively. These results indicate that the degree of deviance modulates spatio-temporal dynamics within the STC-IFC auditory change detection network.