The auditory P2 evoked by speech sounds consists of two separate subcomponents

The P2 component of the auditory evoked potential is commonly thought to reflect acoustic stimulus properties as well as prior exposure to the materials, rather than change-related cortical activity. Here, we challenge this view by showing that the P2 is strongly increased in response to voice pitch changes with a stepwise pattern compared to changes in dynamic pitch contours typical for natural speech, and also reflects the magnitude of these pitch changes. Furthermore, it is demonstrated that neither the P2 nor any other component are affected by the harmonicity of the materials. Despite no prior exposure, artificially created inharmonic versions of the speech materials elicited similar activity throughout auditory cortex. This suggests that so-called harmonic template neurons observed in animal studies are either absent or do not exist in sufficient number in human auditory cortex to detect their activity extracranially. Crucially, both morphology and source reconstructions of the EEG data showed that the P2 appears to consist of two separate subcomponents. Whereas source activity for the "P2a" was strongest in right auditory cortex, the subsequent "P2b" included generators spread across auditory cortex and association areas, bilaterally. The two subcomponents thus likely reflect processing at different stages of the auditory pathway.