Auditory event-related potentials reflect dedicated change detection activity for higher-order acoustic transitions

The processing of auditory changes at cortical level relies partly on dedicated change-detectors whose activity is reflected in the elicitation of the N1 and P2 event-related potentials (ERPs). In previous studies, N1 and P2 have been found only for first-order frequency transitions (i.e. constant-to-glide) but not for higher-order transitions (i.e. glide-to-constant). We tested whether this asymmetry is due to the complete lack, or the smaller number of dedicated higher-order change detectors compared to first-order change detectors by recording ERPs to constant-to-glide and glide-to-constant frequency transitions within pure and complex tones. For constant-to-glide transitions ERP amplitudes increased with the rate of frequency change and spectral complexity. Importantly, for glide-to-constant transitions, N1 was elicited, even though only for spectrally rich tones when the frequency-change rate was fastest. Thus, the asymmetry in auditory change-related N1 elicitation is attributable not to the lack of higher-order change detectors, but to their relatively low number.