Test-retest reliability of a functional MRI working memory paradigm in normal and schizophrenic subjects

Objective: Repeated functional magnetic resonance imaging (fMRI) studies of schizophrenic subjects may identify brain activity changes in response to interventions. To interpret the findings, however, it is crucial to know th e test-retest reliability of the measures used. Method: The authors scanned seven normal subjects and seven schizophrenic s ubjects on two occasions during performance of a working memory task. They quantified the reliability of task performance and brain activation. Results: In both groups, task performance was reliable, and all a priori re gions were activated in group-averaged test and retest data. In individual schizophrenic subjects, however, indices of cognitive activation were not r eliable across sessions. Normal subjects showed reasonable reliability of a ctivation. Conclusions: Even given reliable task performance, stable clinical status, and a stable pattern of group-averaged activation, individual subjects show ed unreliable brain activation. This suggests that repeated fMRI studies of schizophrenia should control for sources of variation, both artifactual an d intrinsic.