The architecture of cognitive control in schizophrenia.

Executive dysfunctions have long been considered a common feature of schizophrenia. However, due to their extreme heterogeneity, it is not clear whether these impairments take place at a particular level of executive functioning or non-specifically affect various aspects of behavioural control. To answer this question, we used an experimental paradigm based upon a multistage model of prefrontal executive function. This model postulates that cognitive control is organized in three hierarchically ordered control processes, operating with respect to the perceptual context (sensory and contextual controls) or the temporal episode in which the person is acting (episodic control). Twenty-four patients with schizophrenia and 24 non-psychiatric controls participated in two distinct experiments designed to separately assess each of these three levels of control. The results indicate that both sensory and episodic dimensions of cognitive control were spared in schizophrenic patients, but that they showed great difficulty in contextual conditions, as the selection of the appropriate response among competitive ones required taking into account information related to perceptual context. Contextual control can be considered as a set of executive processes mediating the hierarchical organization of behaviour. Patients' deficit in cognitive control therefore reflects a specific problem in the hierarchical control of action, leading to the selection of inappropriate behavioural representations for ongoing action plans. We also showed that this impairment was a good predictor of disorganization syndrome scores, suggesting that these clinical manifestations might result from a deficit in the combination or selection of hierarchically organized action representations.