Impairment in error monitoring predicts poor executive function in schizophrenia patients

Background: Impaired ability to detect and correct errors may contribute to poor cognitive and social function in schizophrenia. Objective: To test the hypothesis that impairment in error monitoring contributes to impaired executive function in schizophrenia. Methods: 56 schizophrenia patients and 77 healthy individuals were tested with the Penn Conditional Exclusion test (PCET), a computerised test of executive function which allowed collection of accuracy and latency performance parameters. Error monitoring was assessed by analyzing reaction times for correct (RTC) and incorrect (RTI) responses. Tests of face recognition, working memory (WM) and processing speed were also administered. Results: Executive error-monitoring effort (EXER), calculated by dividing the difference between RTI and RTC by the sum of RTC and RTI, was significantly smaller in patients than controls. A regression model with the executive function (PCET total errors) as dependent variable showed independent contributions of EXER, verbal WM and spatial WM to test performance and explained 35% of the variance. EXER showed significant association with error-monitoring effort for face recognition in patients but not controls. Conclusion: Impaired error-monitoring contributes to poor executive function in schizophrenia. Independent contributions of error-monitoring effort and verbal WM to executive functions may reflect distinct contributions of prefrontal and medial frontal cortical dysfunctions. Error-monitoring mechanisms in different cognitive domains may share more neural resources in schizophrenia than in healthy individuals, reflecting inefficient processing. (C) 2007 Elsevier B.V. All rights reserved.