Objective: Although deficits in cognitive control are thought to contribute to the diverse cognitive and behavioral abnormalities in individuals with schizophrenia, the neural mechanisms underlying these deficits remain unclear. In this event-related functional magnetic resonance imaging (fMRI) study, the authors tested the hypothesis that during cognitive control tasks, impaired activation of the dorsolateral prefrontal cortex in schizophrenia patients is associated with disrupted coordinated activity between this prefrontal region and a distributed brain network that supports cognitive control.
Method: Through the use of an event-related design, 25 patients with first-episode schizophrenia and 24 healthy comparison subjects, matched on demographic characteristics, were assessed while performing a version of the AX continuous performance task. Functional neuroimaging data were analyzed using 1) univariate (region-of-interest blood-oxygen-level-dependent [BOLD] time series and whole brain voxel-wise regression) analysis to confirm the presence of dorsolateral prefrontal cortex dysfunction and 2) multivariate analysis to examine dorsolateral prefrontal cortex functional connectivity. In addition, correlations between dorsolateral prefrontal cortex functional connectivity and the following variables were investigated: clinical symptoms, task performance, and coordinated brain activity associated with cognitive control.
Results: Schizophrenia patients exhibited a specific deficit in cognitive control, with significantly reduced accuracy in the BX condition relative to any other condition. Univariate fMRI revealed dorsolateral prefrontal cortex dysfunction during the high cognitive control condition. Multivariate analysis revealed significant impairment in functional connectivity between the dorsolateral prefrontal cortex and task-relevant brain regions. Significant correlations were also found between dorsolateral prefrontal cortex functional connectivity and cognitive performance, behavioral disorganization, and global functioning.
Conclusions: These findings suggest that there is an association between decreased dorsolateral prefrontal cortex activity and connectivity and a task-related neural network. This deficit in coordinated brain activity may result in the disabling disorganization symptoms related to impaired cognition in individuals with schizophrenia.