Impairment of visual working memory as endo-phenotypic marker for paranoid schizophrenia

Abstract

Abstract Background Examination of cognitive endo-phenotypes is a modern approach for establishing genetic risk for schizophrenia. Visual working memory (VWM) is significantly impaired in cases with paranoid schizophrenia (PSch). Benton Visual Retention Test (BVRT) is a standardized neurocognitive instrument for accessing VWM. The aim of the study was to access VWM in patients with PSch and their first-grade relatives (FGR) and to compare the results with healthy controls. Methods We examined VWM in 108 patients with PSch - 66 males and 42 females; their mean age was 38.86±10.02 years and average disease severity 71,8±5,1 points measured on Positive and Negative Syndrome Scale. The FGR group included 30 males and 28 females with a mean age 36.71±11.74 years. The control group consisted of 37 males and 23 females aged 35.68±11.36 years. The VWM in all cases was measured by BVRT. The study was approved by the University of Pleven Ethical Committee. Mann-Whitney U and z-tests were used for between-group comparisons. All correlations were interpreted as significant at 95% confidence level. Data processing was performed by IBM SPSS Statistics v.24. Results Patients with PSch showed lower correct answers and more total errors on BVRT as compared to their first-grade relatives (z= -6.482; p = 0.0001). They also made more omissions, distortions, perseverations, misplacement errors and had specific tendencies for changing angular figures with circles. First-grade relatives had greater total number of errors and more distortions, perseverations, misplacement errors and horizontal shifts compared to healthy controls. All differences were significant at p = 0.01 or even p = 0.001. Conclusions Both PSch and FGR show difficulties in space organization and/or have restricted analysis of perception and poor scheme of getting information. This illustrates a deficit in the hierarchical organization, planning and strategy development for visual perception resulted from the frontal disfunction. Key messages First-grade relatives of patients with paranoid schizophrenia show specific impairments of visual working memory which makes it suitable endo-phenotypic marker for paranoid schizophrenia. Visual working memory could be used in clinical scientific research for the purpose of differentiation of high-risk groups for schizophrenia.