Differential disruptions of working memory components in schizophrenia in an object-location binding task using the suppression paradigm.

Patients with schizophrenia exhibit normal memory for separate objects or locations but are disproportionately impaired when the items must be bound for later recognition in a working memory (WM) setting (Burglen et al., 2004). This study aimed at further evaluating the contribution of each WM component to the patients' binding deficit, using selective articulatory, visuospatial, and executive suppression tasks. In the object-location binding task used, a trial comprised the successive presentation of three drawings of familiar objects and of three spatial locations in a grid, either separately (i.e., objects alone or locations alone) or bound (i.e., object+location), and required a recognition test following an 8-s delay. In the suppression modalities, suppression was continuous from presentation to test. A total of 22 patients with schizophrenia and 24 healthy controls participated. The results confirmed the binding deficit in patients' performance in the baseline modality where no suppression was required. They also showed that patients were particularly disrupted when suppression was visuospatial. This last finding extends the specific visuospatial vulnerability in schizophrenia to the operations of binding.

Impaired performance in a working memory binding task in patients with schizophrenia.

This study investigated feature binding in a working memory task in patients with schizophrenia and in normal controls. Twenty-five patients and 25 controls participated. On each trial, three drawings of familiar objects were presented sequentially, each in a different cell of a 3 x 3 grid. In different blocks of trials, participants remembered either individual features (object and location conditions) or an object and its location (combination condition). The results showed that patients were slower and less accurate than controls under all conditions. Accuracy of both groups was reduced in the combination condition relative to the single-feature conditions, but patients showed disproportionately poorer performance in the combination condition than in the object and location conditions. Thus, patients with schizophrenia exhibit deficits in working memory, particularly when the task requires binding objects to their locations. This finding demonstrates that processes that establish coherent and temporary episodic representations in working memory are impaired in schizophrenia.

Impaired strategic regulation of contents of conscious awareness in schizophrenia.

Conscious awareness comprises two distinct states, autonoetic and noetic awareness. Schizophrenia impairs autonoetic, but not noetic, awareness. We investigated the strategic regulation of relevant and irrelevant contents of conscious awareness in schizophrenia using a directed forgetting paradigm. Twenty-one patients with schizophrenia and 21 normal controls were presented with words and told to learn some of them and forget others. In a subsequent test, they were asked to recognize all the words they had seen previously and give remember, know or guess responses according to whether they recognized words on the basis of autonoetic awareness, noetic awareness, or guessing. Overall, patients showed the same degree of a directed forgetting effect as normal subjects. However, whereas the effect was observed both for remember and know responses in normal subjects, it was observed for know, but not for remember, responses in patients. These results indicate that patients with schizophrenia exhibit an impaired strategic regulation of contents of autonetic awareness for relevant and irrelevant information.