Dysfunctional Neural Processes Underlying Context Processing Deficits in Schizophrenia.

BACKGROUND: People with schizophrenia (PSZ) have profound deficits in context processing, an executive process that guides adaptive behaviors according to goals and stored contextual information. Although various neural processes are involved in context processing and are affected in PSZ, the core underlying neural dysfunction is unclear.
METHODS: To determine the relative importance of neural dysfunctions within prefrontal cognitive control, sensory activity, and motor activity to context processing deficits in PSZ, we examined event-related potentials (ERPs) in 60 PSZ and 51 healthy control subjects during an optimal context processing task. We also analyzed the Ex-Gaussian reaction time distribution to examine abnormalities in motor control variability in PSZ.
RESULTS: Compared with healthy control subjects, PSZ had lower response accuracy and greater variability in their normal reaction times during high context processing demands. Latencies of normal and slow responses were generally increased in PSZ. High context processing-related reductions in frontal ERPs were indicative of specific deficits in proactive and reactive cognitive controls in PSZ, while ERPs associated with visual and motor processes were reduced regardless of context processing demands, indicating generalized visuomotor deficits. In contrast to previous studies, we found that diminished frontal responses reflective of proactive control of the contextual cue, rather than visual responses of cue encoding, predicted response accuracy deficits in PSZ. In addition, probe-related ERP components of motor preparation, prefrontal reactive control, and frontomotor interaction predicted Ex-Gaussian indices of reaction time instability in PSZ.
CONCLUSIONS: Prefrontal proactive and reactive control deficits associated with failures in using mental representation likely underlie context processing deficits in PSZ.