Performance of patients with schizophrenia on a pen and paper visuospatial working memory task with short delay.

Human and nonhuman primate data suggest that visuospatial working memory is mediated by a neural network that includes the prefrontal cortex. Simple working memory tasks are less complex than standard neuropsychological tests of frontal dysfunction. As such, they are less vulnerable to general performance factors such as amotivation and uncooperativeness in schizophrenic patients. These tasks thus hold promise as potential measures of frontal dysfunction in schizophrenia. However, the specific parameters of visuospatial working memory deficit in schizophrenia have not been established. This study assessed working memory functions in 18 schizophrenic patients and 28 controls using a pen-and-paper analogue of a monkey prefrontal cortex activation task. Schizophrenic patients and controls performed similarly on a sensory-guided task that did not require working memory functions, yet schizophrenic patients performed significantly worse than controls on tasks that required subjects to retain visuospatial information for delay periods of 10 and 20 s. These data suggest that the working memory deficits in patients with schizophrenia begin to appear less than 10 s following encoding of visuospatial information and that these working memory deficits can be assessed with easily administered pen-and-paper tasks.