Mapping brain networks underlying abstract perceptual decision formation and its EEG signatures

Perceptual decisions have been proposed to involve a common mechanism of evidence accumulation operating across sensory modalities and motor contexts. In human EEG, the centroparietal positivity (CPP) tracks evidence accumulation in such a supramodal motor-independent manner, but its cortical sources are uncertain. Here we combined fMRI and EEG, acquired in separate sessions of the same supramodal change-detection paradigm, with individualized finite element head modeling to identify decision-related networks. A conjunction analysis across visual and auditory modalities and across motor and non-motor required tasks revealed consistent activation of bilateral postcentral, supramarginal, and superior parietal lobules, precentral gyrus, central operculum, middle frontal gyrus, and cerebellum. Forward modeling of fMRI-defined sources indicated that parietal-opercular regions were the dominant contributors to the response-locked and non-motor-required peak-locked CPP signal. These results implicate a network of brain areas in supramodal, motor-independent target-detection decisions, whose specific functional roles can be interrogated in more complex decision tasks in future.