Processing of auditory stimuli during visual attention in patients with schizophrenia.

BACKGROUND: The aim of this study was to evaluate attentional functioning in patients with schizophrenia with an emphasis on automatic processes using the mismatch negativity (MMN) component of the event-related brain potential.
METHODS: Participants were asked to perform a challenging visual discrimination task and simultaneously ignore auditory stimuli presented in the background. In different blocks of trials, the background was either a sequence of tones that included rare deviant tones differing in pitch or a sequence of tones that alternated regularly in pitch with occasional deviant repetitions. In a second experiment, participants were asked to actively respond to auditory deviant stimuli.
RESULTS: Visual targets generated smaller N1, N2, and P3b deflections in patients than in control subjects, suggesting deficits in controlled attentional processes. Auditory deviant stimuli elicited an MMN that varied in scalp distribution as a function of the deviant-type (pitch vs. pattern). In patients with schizophrenia, impaired auditory discrimination was associated with altered MMN topography and reduced MMN amplitude.
CONCLUSIONS: These findings are consistent with impaired automatic processes in patients with schizophrenia, which may contribute to their difficulties in processing complex auditory sequences. The timing and scalp topography are consistent with impaired auditory pattern analysis in posterior association cortices.