Attention Disorders After Right Brain Damage

Attention Disorders After Right Brain Damage Paolo Bartolomeo Attention Disorders After Right Brain Damage Living in Halved Worlds Paolo Bartolomeo, MD, PhD Brain and Spine Institute Hô pital de la Salpê triè re Institut national de la santé et de la recherche médicale (INSERM) Paris France Department of Psychology Catholic University Milan Italy ISBN 978-1-4471-5648-2 ISBN 978-1-4471-5649-9 (eBook) DOI 10.1007/978-1-4471-5649-9 Springer London Heidelberg New York Dordrecht Library of Congress Control Number: 2013957355 © Springer-Verlag London 2014 This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifi cally the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfi lms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. Exempted from this legal reservation are brief excerpts in connection with reviews or scholarly analysis or material supplied specifi cally for the purpose of being entered and executed on a computer system, for exclusive use by the purchaser of the work. Duplication of this publication or parts thereof is permitted only under the provisions of the Copyright Law of the Publisher's location, in its current version, and permission for use must always be obtained from Springer. Permissions for use may be obtained through RightsLink at the Copyright Clearance Center. Violations are liable to prosecution under the respective Copyright Law. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specifi c statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. While the advice and information in this book are believed to be true and accurate at the date of publication, neither the authors nor the editors nor the publisher can accept any legal responsibility for any errors or omissions that may be made. The publisher makes no warranty, express or implied, with respect to the material contained herein. Printed on acid-free paper Springer is part of Springer Science+Business Media (www.springer.com) Foreword Among the many mysteries of the human brain, one remains the most blatant but least unveiled. Namely, our brain (but also that of other species) is made of two distinct, grossly symmetrical parts – the right and left hemispheres – which enter- tain rich interconnections but also substantial independence and even remarkable specialization (perhaps unlike any other species). Such division of labor contrasts with our subjective sense of unity in thoughts, intentions, perceptions, or memo- ries. This is patent when looking straight ahead in our central visual fi eld: although its representation in occipital visual cortex is split in the midline across the two hemispheres, several centimeters apart, we experience no perceptible discontinuity. This unity of bilaterally distributed neural activities also occurs for our bodily sen- sations and actions, be it when we scratch our belly across the midline or play the piano with two hands, and even more so when we apprehend and explore space around us. Because this unity is so powerful and feels so natural, it often takes a lesion in brain circuits to make the fundamental hemispheric division of our brain more apparent and unfortunately troublesome for brain-damaged patients. Such revealing nature of clinical disorders of cognition and behavior is precisely what makes neuropsychology a unique and irreplaceable approach to understanding the brain and mind. Further, besides basic neuroscience knowledge, in clinical practice, accurate recognition of defi cits specifi c to lesions affecting one or the other hemisphere is a major step for correct diagnosis. For example, neuropsychological signs of right brain dysfunction in a patient with word naming diffi culties may disclose unsus- pected bilateral or multifocal disease such as dementia or multiple sclerosis and thus require totally different clinical investigations. By providing a comprehensive overview of right brain functions and dysfunc- tions, masterfully assembled in a coherent neurocognitive framework, the present volume by Paolo Bartolomeo provides a compelling testimonial for both the clinical and scientifi c importance of pathologies of the right hemisphere. Traditional neurol- ogy terminology has qualifi ed the right side of the human brain as being the “minor” hemisphere, as opposed to the “dominance” of the left for language and manual dexterity. However, as reviewed in this book, the right hemisphere is associated v vi Foreword with a very rich set of functions, many of which actually touch the highest among high-level cognitive abilities. Not only attention and awareness are crucially depen- dent on right hemispheric networks but also space representation, navigation, men- tal fl exibility and inhibitory control, mathematics, face recognition, emotion, music, as well as body ownership and key aspects of self-experience – all are deeply rooted in nonverbal integrative processes mediated by the (so-called) “minor” right hemisphere. These abilities seem in many ways as complex as language or dexterous hand movements, if not more. Moreover, their impairment leads to severe handi- caps in everyday life. Thus, given the many essential functions subtended by the right hemisphere, one may wonder whether neurologists from another civilization (perhaps more attentive to nonverbal abilities) would have conceived this hemisphere as actually being the dominant one, generating the substance of sensory and experiential phenomena that may then be passed on to the subordinate left hemisphere for speech and hand motor outputs. At the very least, in a democratic brain, the right hemisphere should certainly be treated equally to the left and not put in a minority position. Paolo Bartolomeo therefore does full justice to the right hemisphere by devot- ing this new book to the sophisticated cognitive apparatus of this signifi cant half of the brain and its defi ciencies following various pathologies. The book also cogently dissects the intricate relationships of right hemispheric disorders with attention and space. A major focus is put on the neglect syndrome and related dis- abilities, in keeping with the high frequency of such symptoms after right brain damage and their key interest for neuropsychology and cognitive neuroscience of attention processes. The successive chapters provide a complete and articulate coverage of several facets of attentional disorders, from the description of various behavioral phenomena through to the analysis of the underlying cerebral substrates. This systematic review is provided in a very fl uid and synthetic manner, revealing the encyclopedic knowledge and critical perspective of the author. Throughout the book, a remarkable quality is the attempt to relate clinical observa- tions to rigorous experimental measures, link them to precise cognitive mecha- nisms and neuroanatomical substrates, and integrate these data with current theoretical frameworks derived from neuroscience research in both human and nonhuman primates. In this process, the author portrays a compelling model of functional brain networks made of distributed and interactive regional nodes, whose functioning is dynamically shaped by attentional states and differentially impaired by pathology. This perspective does not only help provide a valuable mechanistic account for neglect and other neuropsychological disorders in right- brain-damaged patients but also open useful perspectives for remediation strate- gies. As such, the book will offer a unique resource for clinicians and students eager to learn about neuropsychology and its foundations in more basic brain sci- ences, while it will also supply researchers from various fi elds with a precious source of references and stimulating new ideas, organized with a well- structured manner and critical thinking. In sum, by being a skilled clinician as well as an incisive researcher who made key contributions to current scientifi c knowledge on attention and neglect, and by Foreword vii craftily combining this personal experience with a broader neuroscience literature, Paolo Bartolomeo gives us here an admirable tutorial that clearly demonstrates (and explains) the major functions and disorders of the (not so) minor hemisphere. Geneva, Switzerland Patrik Vuilleumier Preface and Ac knowledgments In a neurological ward, it is frequent to come upon patients who look at objects on their right side with intense interest, while paying no attention to what happens on their left. Left visual neglect is a dramatic but often overlooked consequence of right hemisphere damage, usually of vascular origin, but also resulting from other causes, such as neurodegenerative conditions. Patients do not eat from the left part of their dish, they bump their wheelchair into obstacles situated on their left side, and have a tendency to look at right-sided details as soon as a visual scene deploys, as if their attention were “magnetically” attracted to these details. They are usually unaware of their defi cits (anosognosia) and often obstinately deny being hemiple- gic. Patients with left brain damage may also show signs of contralesional, right- sided neglect, but much more rarely

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