of other modalities than are piriform cortex and related olfactory cortical regions (Haberly, 2001). In this scenario, it is unlikely that neuronal activity of primary olfactory processing, equivalent to calcarine or Heschl’s gyrus activation within the visual or auditory pathways, will propagate to scalp and may therefore not register as an ERP component. Another consideration is that the completely different organization of the olfactory system (e.g., lack of thalamocortical projections, afferent and efferent projections of primary sensory cortex vs. limbic cortex)makes a homology with N1 from othermodalities improbable. Rather, olfactoryN1 sink activity peaking around 300 ms may instead reflect functional activation of secondary olfactory regions, including piriform cortex, analogous to inferior-temporal visual association cortex (see Figure 13 in Haberly, 2001). The implication of this proposition is that N1 sink could be regarded as an olfactory N2, analogous to an auditory or visual N2. In this case, the olfactory N1 should be associated with stimulus categorization and classification, and the sequence of olfactory N1 sink and P2 source in the present odor detection paradigm would be the olfactory equivalent of an N2/P3 complex typically observed during many ERP paradigms, including an oddball task. Although it is not impossible that an olfactoryN1
