Do loudness cues contribute to duration mismatch negativity reduction in schizophrenia?

The present study explored duration mismatch negativity (MMN) reduction in schizophrenia. Duration MMN studies usually employ tones of very short duration (< 200 ms). For stimuli < 200 ms in duration, an increment in duration is accompanied by an increase in perceived loudness. It was previously proposed that the effectiveness of duration MMN in revealing MMN reduction in schizophrenia might be explained by patients being insensitive to loudness cues and duration increments. In this study we equated loudness cues in a typical duration MMN paradigm and explored the effect of this manipulation on MMN amplitude reduction in schizophrenia. The manipulation had little effect on a healthy comparison group but had a marked effect on the MMN generated in the patient group who produced a significantly smaller MMN response to the regular duration deviant than to that in the equated loudness condition. This result was interpreted as demonstrating that patients exhibit a very marked insensitivity to duration increments.