Mismatch negativity to inclusions and omissions of stimulus features

Two experiments were run to determine the effects of addition or removal of a stimulus feature on mismatch negativity (MMN). In the first experiment, a deviant stimulus was constructed by adding a click to a white noise stand ard stimulus. In the second experiment, the deviant was constructed by subt racting the click from the standard. In different conditions, the intensity of the click was varied. When the deviant was constructed by the addition of a click, a significant MMN was evident in those conditions in which clic k-to-noise ratio exceeded 1.0. When the deviant was constructed by the subt raction of the click, a significant negativity was found only when the clic k-to-noise ratio was very large. However, this negativity was accompanied b y only a small polarity inversion at the mastoid. The MMN is thus best elic ited when the deviant stimulus contains a new afferent element not present in the standard stimulus. NeuroReport 11:1503-1507 (C) 2000 Lippincott Will iams & Wilkins.