Temporal order and spatial memory in schizophrenia: a parametric study.

Spatial working memory has been shown to be impaired in schizophrenia. In contrast, memory for temporal order has been poorly studied in patients with schizophrenia. The aim of this study was to compare and to further characterize spatial working memory and sequence reproduction deficits in patients with schizophrenia under stable medication by manipulating cues (pattern versus sequence), delay, set-size and response type in various recall and recognition tasks. This allowed us to dissociate processes as encoding, retention and retrieval and to compare the performance of patients with schizophrenia to the performance of patients with prefrontal lesions, who have been previously tested in the same tasks. Our results show that increase of the set-size and of the delay decreased performance of both groups, and that these factors had larger detrimental effects in patients with schizophrenia than in controls. Furthermore, comparison between tasks revealed retention and retrieval deficits in schizophrenia. Finally, patients with schizophrenia showed impairments not only in recall but also in sequence recognition tasks with delay. This is in contrast to patients with prefrontal lesions, who have previously been shown to have intact recognition of sequences after a delay. These results suggest that the working memory deficit in schizophrenia cannot be restricted to a prefrontal dysfunction.