Differential Relationships of Mismatch Negativity and Visual P1 Deficits to Premorbid Characteristics and Functional Outcome in Schizophrenia

Background: Mismatch negativity (MMN) and visual P1 are established event-related potential (ERP) markers of impaired auditory and visual sensory function in schizophrenia. Differential relationships of these measures with premorbid and present function and with clinical course have been noted previously in independent cohorts, but measures have not yet been compared within the same patient group. Methods: Twenty-six schizophrenia patients and 19 control subjects participated in a simultaneous visual and auditory ERPs experiment. Attended visual ERPs were obtained to low-and high-spatial frequency stimuli. Simultaneously, MMN was obtained to unattended pitch, duration, and intensity deviant stimuli. Premorbid function, symptom, and global outcome measures were obtained as correlational measures. Results: Patients showed substantial P1 reductions to low-but not high-spatial frequency stimuli, unrelated to visual acuity. Patients also exhibited reduced MMN to all deviant types. No significant correlations were observed between visual ERPs and premorbid or global outcome measures or illness duration. In contrast, MMN amplitude correlated significantly and independently with premorbid educational achievement, cognitive symptoms, global function, and illness duration. The MMN to duration versus other deviants was differentially reduced in individuals with poor premorbid function. Conclusions: Visual and auditory ERP measures are differentially related to the pathophysiology of schizophrenia. Visual deficits correlate poorly with functional measures and illness duration and serve primarily as trait vulnerability markers. The MMN deficits are independently related to premorbid function and illness duration, suggesting independent neurodevelopmental and neurodegenerative contributions. The lack of correlation between auditory and visual ERPs in schizophrenia suggests contributions from divergent underlying neurophysiological processes.