The mismatch negativity as an index of temporal processing in audition

Objectives: The relation of the mismatch negativity (MMN) elicitation with behavioral stimulus discrimination as well as the replicability of the MMN was evaluated for intervals between paired tones. Methods: The MMN, obtained in a passive oddball paradigm in two sessions separated by 4–21 days and behavioral responses (button presses to target stimuli) in a separate session were recorded from 10 adult healthy subjects. The standard stimulus (P=0.79) was a tone pair separated by a 120 ms silent inter-stimulus interval (ISI) and the deviant stimuli were tone pairs with an ISI of 100, 60, and 20 ms (P=0.07 for each). Results: The 20 and 60 ms ISI deviant tone pairs elicited a significant MMN during both recording sessions and they were also behaviorally discriminated, whereas neither did the 100 ms ISI deviant pair elicit significant MMN nor was it behaviorally discriminated. Furthermore, there was a significant correlation between the MMN and reaction times to the 20 and 60 ms ISI deviant pairs. The 20 ms ISI deviant stimulus elicited highly replicable MMNs (r=0.75), whereas the less well discriminated 60 ms ISI deviant pair did not (r=0.60). Conclusions: The MMN reflects discrimination accuracy of temporal sound intervals. Furthermore, when the physical difference between the standard and deviant tone pair in the temporal domain is large, it is elicited with high reliability.