Is there a mismatch negativity analogue in the olfactory event-related potential?

The mismatch negativity (MMN) is thought to indicate automatic stimulus discrimination in response to acoustic stimuli. In the present study six male subjects were presented with the odors linalool and eugenol within a passive oddball-paradigm. The subjects were instructed to ignore the odors and concentrate on an auditory distracter task. In two sessions each odor served once as the standard stimulus and once as the deviant stimulus. Both odors when presented as deviants led to a negative deflection of the olfactory event-related potential (OERP) between 500-600 ms. After 600 ms the waveforms in response to the deviants were differentially influenced by odor quality. Although the present study should be understood as exploratory, the results suggest the existence of an early mismatch detector in the olfactory modality independent of attention and odor quality.