Although the nature and significance of the later components is beyond the scope of this paper, the CSD also offers clear advantages over ERPs for the late, condition-dependent components (i.e., prominent for rare targets requiring a right hand response compared to frequent nontargets). First, the sinks corresponding to N2 (260 ms) and the frontal response-related negativity (FRN; 500 ms) are considerably more prominent and topographically distinct in the CSD waveforms and topographies than are the negativities in either of the reference-dependent ERPs. Second, the well-defined P3 source (360 ms in Fig. 4A) contrasts with the marked differences between nose- and mastoid-referenced ERPs at all locations. Third, the localization and asymmetry of the late response-related components are most distinctive for the CSD (cf. Fz, C3, C4 in Fig. 4A), revealing a robust, persistent negativity over, but not confined to, the left motor cortex (i.e., contralateral to the response hand) and a robust, focal mid-frontal sink at the approximate time of the button press. Furthermore, the response-related, contralateral negativity is superimposed on P3, revealing a characteristic source asymmetry over central sites, that
