Background: Schizophrenia patients exhibit widespread deficits in many domains, ranging from abnormalities in preattentional sensory processing to gross impairments in everyday functioning. Mismatch negativity (MMN) is an event-related potential measure that occurs in the absence of directed attention. While many studies have reported MMN deficits in schizophrenia patients, little is known about the functional significance of MMN deficits in schizophrenia patients.
Objective: To determine if a schizophrenia-linked deficit in MMN, an "automatic" preattentional measure, is associated with impairments in everyday functional status, level of independence in living situation, and the ability to perform tasks routinely encountered in everyday situations.
Setting and participants: Twenty-five patients with a DSM-IV diagnosis of schizophrenia recruited from inpatient and outpatient community facilities affiliated with the University of California, San Diego, and 25 healthy, nonpsychiatric, comparison subjects.
Main outcome measures: Mismatch negativity, clinical symptoms, performance on a multidimensional laboratory-based functional skills assessment battery, clinician ratings on the Global Assessment of Functioning Scale, and level of independence in community living situation.
Results: Schizophrenia patients had significantly reduced MMN (P<.001). Greater levels of MMN impairment were associated with lower Global Assessment of Functioning Scale ratings. Consistent with clinical ratings, patients with greater MMN impairments were more likely to live in highly structured vs independent settings. A regional analysis of MMN revealed that the largest correlations of MMN to everyday functioning were present at frontocentral recording sites (eg, r(s) = -0.65). In contrast, MMN deficits were not associated with symptom severity or performance on laboratory-based tasks measuring skills that are often considered necessary for independent living.
Conclusions: This pattern of results suggests that MMN deficits represent a core neurophysiological dysfunction that is linked to global impairments in everyday functioning in schizophrenia patients. These deficits in automatic preattentive information processing account for up to 42% of the variance in global functional status in schizophrenia patients. Thus, basic preattentional cognitive deficits may be excellent measures for predicting functional outcome. Longitudinal studies are needed to better understand the relationships between deficits in automatic sensory information processing, associated neural substrate dysfunctions, and deficits in everyday functioning across the course of the illness.