Deviant matters: duration, frequency, and intensity deviants reveal different patterns of mismatch negativity reduction in early and late schizophrenia

Background: A reduction in the size of the auditory event-related potential component known as mismatch negativity (MMN) is a consistent finding in schizophrenia. This study was designed to test the hypothesis that sound intensity and duration might be more sensitive to MMN reduction early in the development of schizophrenia because of the computational complexity in extracting these two sound dimensions. Methods: The MMN elicited to sounds deviating in duration, frequency, or intensity was measured in participants with a short (n = 14, mean 2.6 years) and longer length of illness (n = 29, mean 18.9 years) relative to healthy age-matched control subjects. Results: For participants early in the illness, a clear reduction was evident in MMN to duration and intensity but not frequency deviants. A different pattern was observed in patients with a longer length of illness - that is, a reduction in frequency and in duration to a lesser degree but not intensity MMN. Conclusions: The results indicate a pronounced age-related decline in duration and intensity MMN in control subjects that might reduce the sensitivity of these indices in schizophrenia when measured later in the course of the illness. The MMN elicited to changes in different sound properties provides potentially complementary information on the onset and progression of neuropathological changes that underlie the reduction in MMN in schizophrenia