“…Two magnetoencephalographic (MEG) studies showed that the magnetic counterpart of MMN (MMNm) was elicited when a regular presentation of FM glides was violated by a change in the FM direction (i.e., rising vs. falling), suggesting that the auditory system was able to preattentively extract the abstract relationship between frequency transitions (Pardo & Sams, 1993;Sams & Näätänen, 1991). However, by using complex FM sweeps with a Gaussian envelope to control for differences in the initial frequency, two recent MEG studies showed that the processing of complex FM sweeps led to repetition enhancement at short interstimulus intervals (ISIs: Altmann et al, 2011;Heinemann, Rahm, Kaiser, Gaese, & Altmann, 2010), but failed to observe MMNm when the acoustic regularity was violated (Altmann et al, 2011).…”