(2008) demonstrated that highly probable repetitions of face pictures lead to a significantly smaller blood oxygen level-dependent contrast than improbable repetitions. Other studies have then replicated the interaction between repetition and repetition probability (Summerfield et al., 2011; Todorovic et al., 2011). Very little is known about the extraction of repetition probability as a higher-order regularity. We adapted the design by Sussman & Winkler (2001) to verify whether constancy in tone onset modulates first-order prediction error, or facilitates CDK inhibitor the formation of higher-order sensory predictions based on deviant repetition probability. The available evidence is inconclusive. At slow stimulation

rates (≤ 2 Hz), irregularity in stimulus-onset time appears to hinder standard repetition effects, i.e. first-order prediction, in complex sequences (Costa-Faidella et al., 2011),

but does not affect the MMN to pitch deviants (Schwartze et al., 2011). Slow stimulation rates may be suboptimal to investigate between-sound relationships as reflected by the MMN response, including temporal ones (Yabe et al., 1998; Sussman & Gumenyuk, 2002; Wacongne et al., 2012). Target Selective Inhibitor Library mw Thus, to tackle our research question, we embedded highly probable (predictable) and less probable (unpredictable) deviant repetitions within isochronous (regular onset) and anisochronous (irregular onset) fast sequences. Fifteen healthy volunteers (seven female, mean age 25.7 ± 3.6 years, range 20–30 years) participated in the study for paid compensation or course credit. All participants self-reported normal hearing, no history of neurological or psychiatric disorders, and no medication affecting the CNS. Participants

gave their written informed consent according to the Declaration of Helsinki. Their data were analysed anonymously. Participants were assigned a progressive numerical code, which did not include information about their identity. We followed the ethical guidelines of The German Psychological Society (‘Deutsche Gesellschaft für Psychologie’, DGPs: http://www.dgps.de/dgps/aufgaben/ethikrl 2004.pdf). Thus, this experiment did not require any additional ethical approval. The stimuli were two sine tones, a 500-Hz standard tone and a 560-Hz deviant tone (Δf = ˜2 semi-tones pheromone in the even-tempered scale), binaurally presented via headphones in pseudo-randomized oddball series, with the constraint that at least two standard tones appeared before a deviant. Tones were played at an intensity of 55 dB sensation level. Hearing thresholds for the standard tone frequency were individually measured using a detection task alternated twice for each ear (for details on the procedure, see Kaernbach, 1990). Within- and between-ear threshold differences never exceeded 10 dB. Tone duration was 50 ms, including 5 ms rise and 5 ms fall times. Tone sequences were presented using Cogent2000v1.25 (Cogent 2000 Team, University of London, UK).