Objective: Functional magnetic resonance imaging was used to study changes in cerebral blood oxygenation in schizophrenic patients during a verbal fluency task.
Method: Five right-handed male schizophrenic patients and five volunteers matched on demographic variables and verbal fluency performance participated in the study. Echoplanar images were acquired over 5 minutes at 1.5 T while the subjects performed two tasks. The first involved paced silent generation of words beginning with an aurally presented cue letter. This task alternated with paced silent repetition of the aurally presented word "rest." Generic brain activation maps were constructed from individual images by sinusoidal regression and non-parametric hypothesis testing. Between-group differences in the mean power of experimental response were identified on a voxelwise basis by an analysis of covariance that controlled for between-group differences in stimulus-correlated motion.
Results: The comparison group showed significant responses in the left prefrontal cortex, the insula bilaterally, the midline supplementary motor area, and the medial parietal cortex. Compared to those subjects, the schizophrenic subjects showed significantly reduced power of response in the left dorsal prefrontal cortex, the inferior frontal gyrus, and the insula but significantly increased power of response in the medial parietal cortex. In both groups frontal and parietal responses were negatively correlated.
Conclusions: Schizophrenic patients displayed attenuated power of response in several frontal regions during word generation but greater power of response in the medial parietal cortex during word repetition.