Aim: Previous studies on schizophrenia have suggested that context-processing disturbances were one of the core cognitive deficits present in schizophrenia. Schizophrenic patients have a failure either of inhibition strategy and maintenance of visuospatial information (25) in condition of contextual interference. In the present study, we explored the performances of untreated schizophrenic patients with 2 tasks exploring detection and long term retention of complex visual features and field dependence-independence tasks were selected. These abilities involve temporary maintenance of visuospatial information and executive functioning of visual working memory system. Several studies have shown that cognitive deficit may depend on schizophrenic symptomatology. However results remain controversial in determining the specific influence of negative and positive symptomatologies as well as clinical disorganization. Our goal was to explore the processing of spatial context and its relation to disorganized syndrome. This study was approved by the local ethic committee.
Methodology: Thirty-six schizophrenic patients were included according to DSM IV criteria (19 neuroleptic naïve, 17 unmedicated patients during more than 3 months). Thirty-six healthy controls were matched to patients for age, gender and level of education. Absence of axis 1 pathology was attested for controls with SCID-NP. Current symptomatology was evaluated by the Positive and Negative Syndrome Scale (PANSS) (14). Clinical disorganisation was evaluated with the disorganisation score established upon a factorial analysis of PANSS by Lepine and Lançon. Items selected to distinguish the disorganised group were abstraction, disorganization, orientation, and attention.
Procedure: Two tasks of embedded figures were administered individually to patients and controls. The Faverge task (Research of Figures-RF) (10) evaluates the ability to recognize the target from spatial complex geometrical figures. The Group Embedded Figure Task (GEFT - Oltman) assesses the detection and maintenance of visual target and its recognition within a complex figure. Performance between patients and controls were compared with the Student T test. The comparison of two clinical subgroups of disorganized and low disorganized patients and control group was performed with an ANOVA. Tuckey test was used for pairwise comparisons.
Results: We defined two subgroups of patients, disorganized patients (subscore 12, n=17) and low disorganized patients (subscore<12, n=19). Theses 2 subgroups were similar for age and level of education. Concerning the two tasks, there was no significant difference between schizophrenic patients and normal controls. The comparison between subgroups of disorganized and low disorganized patients, for RF task, showed a decrease of correct answers with disorganized patients (p<0.05). For GEFT task, disorganized patients had a decrease of correct answers p<0.01) and more errors (p<0.01) and omissions (p<0.05). The low disorganized patients exhibited for the two tests comparable performance to controls. The disorganized patients had a decrease of right answers (p<0.05) and more errors (p<0.05) than controls for GEFT task and no significant difference for RF. However, with IQ (evaluated with an abstract reasoning test) introduced as covariate, only correct answers for GEFT task remain significant (p<0.05).
Discussion: The weak performance of disorganized schizophrenic patients for two tasks RF and GEFT showed that treatment of visuospatial information was impaired in the first perceptive phase of selection and in the organization of information (RF), especially with the maintenance of visual information in memory (GEFT). By contrast, low disorganized patients demonstrated a correct analytic treatment of elementary processing and visuospatial working memory.
Conclusion: The severity of disorganization influences the visuospatial context processing and visuospatial working memory. These results show the heterogeneity of cognitive functioning regarding to schizophrenic symptomatologies. This difficulty could be related to a problem of central executive functioning in the visuospatial component of working memory, possibly mediated by the dysfunction of dorsolateral prefrontal cortex.