Background:
Elicitation of the mismatch negativity (MMN) occurs when the auditory system detects a mismatch between a current sound and the memory formed of a repetitious sequence. MMN can be conceptualized as occurring when a sound violates the context established by preceding events. Individuals with schizophrenia are known to show impairments in the ability to use context when processing the relevance of an event. In this study, we examined whether this impairment in using context would result in in-sensitivity to the effects of temporal context on MMN. Specifically, we explore how temporal context affects the MMN produced by healthy controls and individuals with schizophrenia.
Method:
Eighteen patients and age- and sex-matched controls were presented with two sound sequences over headphones, with attention directed toward a silent movie with subtitles. In the Fixed stimulus onset asynchrony (SOA) sequence, MMN was measured to a 100-ms duration deviant among 50-ms standard tones at a regular 500-ms SOA. The same tones were used in the jittered SOA sequence, with irregular SOAs ranging from 250 to 750 ms.
Results:
In controls, the MMN elicited by duration deviants with jittered SOA was significantly reduced compared with the same deviant occurring in a sequence with fixed SOA. However, changing temporal context/regularity had no significant impact on the MMN produced by the schizophrenia group.
Conclusions:
The results indicate that individuals with schizophrenia have difficulty encoding and forming a model of the temporal context in which a sound occurs.
