Positive symptoms and duration of illness predict functional laterality and attention modulation in schizophrenia Løberg E-M, Jørgensen HA, Green MF, Rund BR, Lund A, Diseth A ˚ , Øie M, Hugdahl K. Positive symptoms and duration of illness predict functional laterality and attention modulation in schizophrenia. Objective: Dichotic listening (DL) performance in schizophrenia, reflecting hemispheric asymmetry and the functional integrity of the left temporal lobe, can vary with clinical characteristics. Previous studies have not taken the co-linearity of clinical variables into account. The aim of the present study was to evaluate the roles of positive symptoms and duration of illness in DL through Structural Equation Modeling (SEM), thus allowing for complex relationships between the variables. Method: We pooled patients from four previous DL studies to create a heterogeneous group of 129 schizophrenic patients, all tested with a consonant-vowel syllables DL procedure that included attentional instructions. Results: A model where positive symptoms predicted a laterality component and duration of illness predicted an attention component in DL was confirmed. Conclusion: Positive symptoms predicted reduced functional laterality, suggesting involvement of left temporal lobe language processing. Duration of illness predicted impaired attention modulation, possibly reflecting the involvement of frontotemporal networks. E.-M. Løberg 1,2 , H. A. Jørgensen 2 , M. F. Green 3 , B. R. Rund 4 , A. Lund 2 , . Diseth 5 , M. Øie 6 , K. Hugdahl 12 1 Department of Biological and Medical Psychology, University of Bergen, 2 Department of Psychiatry, University of Bergen, Bergen, Norway, 3 UCLA Neuropsychiatric Institute, VA Greater Los Angeles Healthcare System, CA, USA, 4 Institute of Psychology, University of Oslo, Oslo, Norway, 5 Department of Psychosocial Science, University of Bergen, Bergen, Norway and 6 Child and Adolescence Psychiatric Outpatient Clinic, Oppland Hospital, Lillehammer, Norway Key words: attention; dichotic listening tests; laterality; schizophrenia; symptoms Else-Marie Løberg, Bergen Mental Health Research Center, Department of Psychiatry, University of Bergen, Sandviken sykehus, 5035 Bergen, Norway. E-mail: else.marie.loeberg@psych.uib.no Accepted for publication July 19, 2005 Significant outcomes • Clinical variables predicted the performance of patients with schizophrenia on a verbal dichotic listening test. • Abnormal laterality for verbal processing was influenced by positive symptoms. • Attention modulation was influenced by duration of illness. Limitations • The sample consisted of patients from four previous studies. • The statistical method; Structural Equation Modeling, may only be used for confirming, and not generating, hypothesis. • Effects of medication could not be tested directly, only be controlled for, by using medication equivalents which have questionable validity. Introduction The dichotic listening (DL) test with verbal stimuli is a simple, non-invasive behavioral technique which reflects the functional integrity of the left temporal lobe language areas (1–3). The typical finding in healthy adults is a hemispheric asym- metry (laterality) effect based on a left hemisphere Acta Psychiatr Scand 2006: 113: 322–331 All rights reserved DOI: 10.1111/j.1600-0447.2005.00627.x Copyright Ó 2005 Blackwell Munksgaard ACTA PSYCHIATRICA SCANDINAVICA 322