University of Wollongong Research Online University of Wollongong Thesis Collection 1954-2016 University of Wollongong Thesis Collections 2002 Executive dysfunction in schizophrenia Susan Leicester University of Wollongong Follow this and additional works at: https://ro.uow.edu.au/theses University of Wollongong Copyright Warning You may print or download ONE copy of this document for the purpose of your own research or study. The University does not authorise you to copy, communicate or otherwise make available electronically to any other person any copyright material contained on this site. You are reminded of the following: This work is copyright. Apart from any use permitted under the Copyright Act 1968, no part of this work may be reproduced by any process, nor may any other exclusive right be exercised, without the permission of the author. Copyright owners are entitled to take legal action against persons who infringe their copyright. 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For further information contact the UOW Library: [email protected] Executive Dysfunction In Schizophrenia A thesis submitted in partial fulfillment of the requirements for the award of the degree Doctor of Philosophy (Clinical Psychology) from UNIVERSITY OF WOLLONGONG by Susan Leicester (B.Sc. (Hons.)) Faculty of Health and Behavioural Sciences 2002 Thesis Certification I, Susan Leicester, declare that this thesis, submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy, in the Department of Health and Behavioural Sciences, University of Wollongong, is wholly my own work unless otherwise referenced or acknowledged. The document has not been submitted for qualification at any other academic institution. Susan Leicester Acknowledgements I would like to express my gratitude to my supervisor, Dr. Nadia Solowij, who took over the role of supervising my thesis quite late in the research and at a time when I was extremely uncertain about its viability and direction. Dr. Solowij listened to my vacillating arguments and doubts and endured a number of decision changes, all with good humor and patience. I believe that I have benefited enormously by having a supervisor who is incredibly professional and dedicated and for this I am eternally grateful. This was evident in Dr. Solowij’s statistical guidance, her commitment and diligence in proofing the work and her attention to detail. I am also indebted to her for the compassion and understanding that she extended to me throughout the long and difficult process of the thesis. Thanks Nadia. I wish to thank Dr. Allison Fox who helped formulate some of the ideas for this research. If Dr. Fox had not given me the initial encouragement to embark on this research I doubt this thesis would have even begun; let alone reached fruition. I would like to thank Dr. Alistair Lethbridge for coming to my aide on a number of occasions with computer support and more importantly, for sharing his words of wisdom from his own thesis experiences. I am very grateful to the participants of this study, particularly those of Lakeview House. They touched my life in ways that I find hard to describe. I deeply admire the humility, courage and fortitude (and sense of humor!) that many of them displayed in the face of the most distressing clinical symptoms. It is to them that I dedicate this thesis. I would like to thank my beautiful children, Shannon and James, for their encouragement, patience, support and belief in me. Their maturity and wisdom belies their ages. And James, thanks for offering to “throw it on the fire” when it all got a bit out of hand. My parents have loved and supported me from afar. Their encouragement, albeit on the other end of the telephone line, was always there whenever I needed it. II Finally, to David, whose faith and encouragement have been constant. He endured the trials and tribulations of the thesis and has supported me through both its high points and troughs. He often knew just the remedy to salve the wound of the moment. His sensitivity and solid, quiet presence enriches my life and has eased the process of this thesis. Thankyou. Ill Abstract This thesis compared the neuropsychological functioning of 51 people with schizophrenia to 60 normal controls by administering a range of tests representative of executive functioning. The clinical group was impaired, compared to controls, on 53 of the 57 test indices, which provided evidence of executive dysfunction in this disorder. Significantly inferior performance was observed on the Stroop Color and Word Test, Wisconsin Card Sorting Test, Trails A and B, the California Verbal Learning Test, the Tower of London Test, the Controlled Oral Word Association Test, Go No-Go and the Ruff Figural Fluency Test. The major empirical focus of this thesis was to explore the factorial structure of tests representative of executive functioning in a sample with schizophrenia and a normal control group by submitting the data to principal components analysis followed by orthogonal rotation. The aim was threefold: to extract several cognitive constructs representing separate aspects of executive functioning, to identify and elucidate the dimensions of deficit in schizophrenia and to determine the stability of the factor structure identified by Levin and colleagues (1996), in a sample of children with documented head-injuries. Four distinct factors were identified in each of the groups. Inhibition and Conceptual- Planning factors were found in both groups. In the control group a Productivity-Strategy construct was identified which was similar to the Productivity construct which emerged in the clinical group. A Cluster factor unique to the group with schizophrenia was also revealed. The detected factor structures provided validation for the factors identified by IV Levin and colleagues (1996). Inhibition, Planning and Conceptual factors were replicated in all three populations and as such these appear to be robust, dissociable aspects of executive functioning. Differences between the factor structures of the schizophrenia and control groups were further explored by the inclusion of additional variables in the factor analysis to facilitate interpretation of the cognitive constructs. The results suggested that the group with schizophrenia was experiencing volitional deficits such that the ability to make and carry out conscious decisions may have been impaired and additionally, that some sort of aberrant functioning may have been occurring. That is, the switching of certain variables between the factors suggested that some kind of on-line, fluid resource allocation might be occurring. The Tower of London was found to capture unique aspects of functioning in schizophrenia, providing measures of apathy and disinhibition. The stability of the control group solution was supported when the factor structure remained essentially the same as the original structure when the additional variables were added to the analysis, only two new constructs emerged—Clustering and Attention. * Correlation analysis did not reveal any consistent relationships between the factor scores and the two syndrome model of symptom subtypes of schizophrenia or a higher dimensional model, both derived from the PANSS (Kay, Fiszbein, & Opler, 1987). The lack of consistent findings parallels the literature. V This study supports the dissociation of executive functioning into separable components and provides evidence of unique functioning in schizophrenia which may vacillate between apathetic and disinhibited performance on demanding working memory tasks. VI Table of Contents Thesis Certification..................................................................................................................I Acknowledgements............................................................................................................... II Abstract..................................................................................................................................IV Table of Contents.................................................................................................................VII List of Tables.............................................................................................................. XII List of Figures.................................................................................................................. XVII 1 INTRODUCTION: THE NOSOLOGICAL CONCEPT OF SCHIZOPHRENIA 1 2 COGNITIVE IMPAIRMENTS IN SCHIZOPHRENIA........................................... 9 2.1 General Cognition....................................................................................................... 10 2.2 Age Effects....................................................................................................................13