Temporal grouping affects the automatic processing of deviant sounds

The present study investigates the influence of auditory temporal grouping on automatic sound processing. We compared the mismatch negativity (MMN) event-related potential elicited by successive deviant tones in a condition in which sounds were organized in tone pairs with respective MMN obtained in a non-paired sequence. When successive deviants belonged to different tone pairs the second deviant elicited a higher MMN amplitude than the corresponding deviant in the non-paired condition. Moreover, this temporal grouping had immediate effects on the extraction of rules as revealed by the finding that first and single deviants at the second position of a tone pair elicited larger MMNs than corresponding deviants in the non-paired condition or first and single deviants at the first position of a tone pair. Results demonstrate that auditory objects generated by temporal proximity are treated as relatively encapsulated units and that automatic deviance-detection may rely on multiple hierarchically organized representations of sound sequences.