Perceptional and executive deficits of chronic schizophrenic patients in attentional and intentional tasks.

The present study investigated whether schizophrenic patients could develop appropriate visual orientation and motor set under precuing conditions which contrasted attentional (input selective) and intentional (output selective) information. The aim was to evaluate perceptual performance in processing visuospatial information, and executive performance in response preparation. Stimuli and/or elicited responses were controlled for selective hemispheric engagement. Age, sex and handedness matched groups of 33 chronic schizophrenic patients and 33 normal subjects were tested on choice reaction time (RT) tasks in which warning signals were manipulated regarding either where a target stimulus would occur (selective attention) or which hand to use for responding (response preparation). All subjects benefited from precued information regarding subsequent responses. However, schizophrenic patients were not able to use intentional cues as effectively as control subjects did. Interhemispheric asymmetry of spatial attention was found in patients with schizophrenia, with slowing of responses to uncued targets presented in the right visual field. There was also a decreased advantage of within-hemisphere stimulus-response conditions in the schizophrenic group. Our results support the notion that a dysfunction involving parietal and premotor areas has potential importance in the schizophrenic illness. We replicated findings which indicate that deficits of information processing in schizophrenia may affect left hemispheric mechanisms to a larger extent. The results also point toward a possible abnormal connectivity between frontal and parietal circuits in schizophrenia.