Mismatch negativity to inclusions of noise within complex spectrotemporal sound patterns.

Event-related potentials to complex spectrotemporal sound patterns were recorded during non-attend conditions. A high-intensity noise deviant elicited a large negative wave. This is probably a combined mismatch negativity (MMN) and N2b since it was followed by a large amplitude frontal positive wave (P3a). When the noise intensity was reduced, a smaller amplitude negative wave was elicited. This probably corresponds to a true MMN since it was not followed by the positive wave. These findings are consistent with previous research in which N2b is elicited in non-attend conditions when the deviant stimulus was particularly difficult to ignore. These findings demonstrate that complex spectrotemporal sound patterns are represented in auditory memory and that inclusions of noise within these complex stimuli can be passively discriminated.