The parametric manipulation of odor intensity in the current study, combined with a non-odor (blank air) control condition, and the use of a denser EEG montage and unbiased randomization tests allowed an improved characterization of the regional activation patterns of odor perception. Hence, N1 sink was most prominent over lateral frontotemporal sites, particularly the left hemisphere, and had corresponding mid-frontopolar, mid-frontocentral and inferior-occipital sources. The increase in odor intensity was strongly paralleled by increases in N1 sink, and to a lesser degree by increases in the corresponding mid-frontocentral and inferior-occipital sources, but not in the mid-frontopolar source. P2 source was broadly distributed over mid-frontocentral and mid-parietal sites, and had corresponding sinks at inferior frontotemporal, frontopolar, and occipital sites. P2 source also showed a monotonic increase in amplitude with increases in odor intensity, and so did the corresponding sinks at inferior sites, but the strength of this association was weaker compared to N1 sink. Both of these scalp CSD patterns are entirely consistent with assumed generator activity within primary and secondary olfactory cortices (i.e., piriform cortex and orbitofrontal cortex), and possibly additional contributions from insular cortex, amygdala, hippocampus and anterior cingulate gyrus (cf. Seubert et al., 2013).
