Validation of a Modified Stroop Task for fMRI Studies in Patients With Schizophrenia

Daniel Antonius; Karen A. Nolan; Elisabeth M. Weiss

Daniel Antonius
Karen A. Nolan
Elisabeth M. Weiss

Abstract

Numerous studies have reported asso- ciations between poor performance on neuropsy- chological measures of executive functions and antisocial behavior. These findings are supported by neuroimaging studies that report prefrontal corti- cal abnormalities in aggressive subjects. Epidemiological studies indicate that patients diag- nosed with schizophrenia perform poorly on execu- tive tasks and are at higher risk for violent behavior than those without mental illness. These data sug- gest that aggression in schizophrenia may be the result of prefrontal abnormalities, and consequent executive dysfunction. A widely used measure of executive functioning is the Stroop paradigm, which requires frontally-mediated cognitive processes such as response inhibition, interference resolution and behavioral conflict resolution. However, implementation of the task, in its traditional form, is prob- lematic for fMRI research. Verbal responses can introduce movement artifacts and the use of covert responses limits evaluation of subjects’ perform- ance. In this ongoing study the investigators are validating a modified version of the Stroop task for use in fMRI experiments with violent and non-vio- lent schizophrenic patients and healthy controls. The modified task requires subjects to respond to directional stimuli by means of a 2-choice button press. Verbal and nonverbal stimuli are presented either alone (neutral condition) or together (congru- ent and incongruent conditions). Preliminary results from 9 patients indicated robust interference effects in terms of both accuracy and reaction time. Final results from patients and controls are presented and their implication for the use of this new test in future fMRI research is discussed. Schizophrenia Research, 60 (supl), 122.

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