Schizophrenia Bulletin Advance Access published online on August 24, 2009
Schizophrenia Bulletin, doi:10.1093/schbul/sbp084
Visual Organization Processes in Schizophrenia
2 INSERM U666, Centre Hospitalier Régional de Strasbourg, Department of Psychiatry I, Hôpital Civil, 1, place de l'Hôpital, 67091 Strasbourg Cedex, France
1 To whom correspondence should be addressed; tel: 00333-88-11-64-61, fax: 00333-88-11-64-46, e-mail: giersch{at}alsace.u-strasbg.fr
Patients with schizophrenia are known to be impaired at organizing and exploring the visual environment. However, these impairments vary across studies, and the conditions determining whether patients are impaired or not are unclear. We aim to clarify this question by distinguishing different types of visual organization processes. A total of 23 patients and matched controls had to identify 2 identical figures embedded in a global structure made of connectors linking figures by pairs. The 2 targets belonged to either the same perceptual group (linked by a connector) or 2 different pairs (not linked by a connector). In a neutral condition, no connectors were presented. Top-down processes were explored by manipulating the proportion of targets linked or not by a connector in 3 experimental blocks. Patients needed the same processing time as controls to extract targets linked by a connector from the global structure. They could also focus on connectors when incited to do so. Impairments were observed for targets that were part of different pairs. Extracting such targets is effortful and time consuming, and both groups were slower in this condition than in the neutral condition. However, patients were slowed less than controls. This paradoxical improvement illustrates the fact that patients do not structure visual elements that are part of a global structure and not automatically bound together. Our results suggest this is due to impaired top-down processes.
Keywords: visual perception / grouping / attention / inhibition