Processing of an obligatory phonotactic restriction outside the focus of the participants' attention was investigated by means of ERPs using (reversed) experimental oddball blocks. Dorsal fricative assimilation (DFA) is a phonotactic constraint in German grammar that is violated in *[ɛx] but not in [ɔx], [ɛ∫], and [ɔ∫]. These stimulus sequences engage the auditory deviance detection mechanism as reflected by the MMN component of the ERP. In Experiment 1 ( n = 16), stimuli were contrasted pairwise such that they shared the initial vowel but differed with regard to the fricative. Phonotactically ill-formed deviants elicited stronger MMN responses than well-formed deviants that differed acoustically in the same way from the standard stimulation but did not contain a phonotactic violation. In Experiment 2 ( n = 16), stimuli were contrasted such that they differed with regard to the vowel but shared the fricative. MMN was elicited by the vowel change. An additional, later MMN response was observed for the phonotactically ill-formed syllable only. This MMN cannot be attributed to any phonetic or segmental difference between standard and deviant. These findings suggest that implicit phonotactic knowledge is activated and applied in preattentive speech processing.

Setting perceptual expectations can be based on different sources of information that determine which functional networks will be involved in implementing preparatory top–down influences and dealing with situations in which expectations are violated. The goal of the present study was to investigate and directly compare brain activations triggered by violating expectations within two different task contexts. In the serial prediction task, participants monitored ordered perceptual sequences for predefined sequential deviants. In contrast, the target detection task entailed a presentation of stimuli which had to be monitored for predefined nonsequential deviants. Detection of sequential deviants triggered an increase of activity in premotor and cerebellar components of the “standard” sequencing network and activations in additional frontal areas initially not involved in sequencing. This pattern of activity reflects the detection of a mismatch between the expected and presented stimuli, updating of the underlying sequence representation (i.e., forward model), and elaboration of the violation. In contrast, target detection elicited activations in posterior temporal and parietal areas, reflecting an increase in perceptual processing evoked by the nonsequential deviant. The obtained results suggest that distinct functional networks involved in detecting deviants in different contexts reflect the origin and the nature of expectations being violated.

The effects of familiarity on auditory change detection on the basis of auditory sensory memory representations were investigated by presenting oddball sequences of sounds while participants ignored the auditory stimuli. Stimulus sequences were composed of sounds that were familiar and sounds that were made unfamiliar by playing the same sounds backward. The roles of frequently presented stimuli (standards) and infrequently presented ones (deviants) were fully crossed. Deviants elicited the mismatch negativity component of the event-related brain potential. We found an enhancement in detecting changes when deviant sounds appeared among familiar standard sounds compared when they were delivered among unfamiliar standards. Familiarity with the deviant sounds also enhanced the change-detection process. We suggest that tuning to familiar items sets up preparatory processes that affect change detection in familiar sound sequences.