A sustained deviance response evoked by the auditory oddball paradigm.

OBJECTIVE

Previous studies have suggested that the MMN(m) is related to selective adaptation of the N(1m). Since selective adaptation has also been reported for the sustained field, we hypothesized a second deviance response in addition to the MMN(m). The present study evaluated the existence of this wave.

METHODS

Magnetoencephalography was used to record deviance responses for pure tones of 1000 and 1050Hz. Tone duration was 50, 150, or 600ms in separate sets. Our hypothesis was that a sustained deviance response would increase with tone duration.

RESULTS

The data revealed a sustained deviance response with a similar source configuration as the main MMN(m), but a distinct time course. The sustained deviance response increased with the tone duration, but less than the standard sustained field. Moreover, the sustained deviance response was already present for short (50ms) tones.

CONCLUSIONS

The MMN(m) is followed by a sustained deviance response in the oddball paradigm. While some characteristics of the response coincide with the sustained field, its growth with tone duration differs. The response could possibly be related to automatic orienting of attention, but further studies are required to explore its functional role.

SIGNIFICANCE

The sustained deviance response is a separate component--distinct from the MMN(m) and P3--that needs to be considered in the evaluation of data obtained with the auditory oddball paradigm.