203 – How cognitive control is implemented in the prefrontal cortex of patients with schizophrenia

Abstract

Background: Deficits of cognitive control (the ability to coordinate thoughts and actions in relation with internal goals) are incriminated to be at the core of the severe and multiple cognitive deficits observed in schizophrenia. The lateral prefrontal cortex was often cited to be responsible for these deficits. However, until now, researchers failed in identifying the precise functional architecture of schizophrenia's cognitive control. Recently, Koechlin et al. showed that the lateral prefrontal cortex (LPFC) is organized as a cascade of executive processes, from premotor to anterior prefrontal areas, that control behavior according to distinct information: sensory information, contextual information (i.e. present perceptual context) and episodic information (i.e. temporal episode in which stimuli occur) respectively. This study aimed at determining which levels of cognitive control are specifically impaired and which prefrontal area is dysfunctional in schizophrenia. Methods: We used functional magnetic resonance imagery to investigate the cerebral correlates of the contextual and episodic controls in 15 schizophrenic patients and 14 control subjects. Results: In normal subjects, as expected, contextual control was only subserved by caudal LPFC, whereas episodic control was subserved by the rostral LPFC. In schizophrenic patients, although a significant increase of error rates compared to controls, the same pattern of prefrontal cortex activations was observed. However, controls recruited bilateral caudal LPFC to a significantly greater extent than patients when subjects had to control contextual information. Conclusions: Our study demonstrates that episodic and contextual controls are specifically impaired in schizophrenia. This impairment is specifically associated with a caudal LPFC dysfunction. These results allow a better understanding of the pathophysiology of some symptoms of schizophrenia.