Visual information-processing impairments in deficit and nondeficit schizophrenia

Previous studies of covert visuospatial attention in schizophrenia suggest a subtle form of right hemispatial neglect in acutely ill patients but not in chronic, stable patients. Because of previous work documenting various visual information-processing abnormalities in deficit schizophrenia, the authors investigated whether the deficit/nondeficit categorization would help clarify the presence of visual attentional asymmetries in schizophrenia.

Performance on a covert visuospatial attention task was examined in clinically stable outpatients with schizophrenia (17 in a deficit subgroup and 28 in a nondeficit subgroup) and 25 normal subjects. Peripheral cue and central cue versions of the covert visuospatial attention task, at 100-, 200-, and 800-msec intervals between cue and target, were administered a week apart.

The nondeficit patients exhibited a significant and abnormal asymmetry, with slower reaction time to targets presented in the right visual field than in the left visual field. This right visual field disadvantage was found with both versions of the task, but only at the 100-msec cue-target interval. The deficit patients were slowest in overall reaction time but, similar to the normal subjects, showed no asymmetry.

The results are consistent with slower visual information processing in the left compared to the right cerebral hemisphere in nondeficit schizophrenia. This finding cannot be accounted for by differences between the deficit and nondeficit subgroups in demographic characteristics, chronicity, or medication effects, nor is it secondary to generalized cognitive impairment.