Apart from replicating the original findings of Turetsky et al. (2003) with a considerably larger sample, the current study advances olfactory ERP research by providing a complete, comparative topographic analysis of reference-independent current source densities underlying reference-dependent surface potentials. The PCA-based summary of orthogonal variance contributions identified a distinct, bilateral temporal N1 sink that appears to be unique to olfactory stimuli. This PCA-CSD component has a subtle ERP counterpart with similar topography that has not yet been reported in the literature, presumably because the common choice of a linked–mastoids reference attenuates the visibility of this topographic effect. In contrast, the topography of P2 source, the second prominent PCA-CSD component, was found to be highly similar to P3 source topographies observed for other stimulus modalities. The topographic CSD findings and insights for olfactory N1 and P2 are unique and may help stimulate methodological and theoretical advancements in the field.
