DOCSLIB.ORG

Evidence for Cortical “Disconnection” As a Mechanism of Age-Related Cognitive Decline

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Evidence for Cortical “Disconnection” As a Mechanism of Age-Related Cognitive Decline 30. Urenjak J, Williams SR, Gadian DG, et al. Proton nuclear 32. Nitsch RM, Blusztajn JK, Pittas AG, et al. Evidence for a magnetic resonance spectroscopy unambiguously identifies membrane defect in Alzheimer disease brain. Proc Natl Acad different neural cell types. J Neurosci 1993;13:981–989. Sci USA 1992;89:1671–1675. 31. Stokes CE, Hawthorne JN. Reduced phosphoinositide concen- 33. Young LT, Kish SJ, Li PP, et al. Decreased brain [3H]inositol trations in anterior temporal cortex of Alzheimer-diseased 1,4,5-triphosphate binding in Alzheimer’s disease. Neurosci brains. J Neurochem 1987;48:1018–1021. Lett 1988;94:198–202. Evidence for cortical “disconnection” as a mechanism of age-related cognitive decline M. O’Sullivan, MRCP; D.K. Jones, PhD; P.E. Summers, PhD; R.G. Morris PhD; S.C.R. Williams, PhD; and H.S. Markus, DM Article abstract—Background: Normal aging is accompanied by a decline of cognitive abilities, and executive skills may be affected selectively, but the underlying mechanisms remain obscure and preventive strategies are lacking. It has been suggested that cortical “disconnection” due to the loss of white matter fibers may play an important role. But, to date, there has been no direct demonstration of structural disconnection in humans in vivo. Methods: The authors used diffusion tensor MRI to look for evidence of ultrastructural changes in cerebral white matter in a group of 20 elderly volunteers with normal conventional MRI scans, and a group of 10 younger controls. The older group also underwent neuropsycho- logical assessment. Results: Diffusional anisotropy, a marker of white matter tract integrity, was reduced in the white matter of older subjects and fell linearly with increasing age in the older group. Mean diffusivity was higher in the older group and increased with age. These changes were maximal in anterior white matter. In the older group, anterior mean diffusivity correlated with executive function assessed by the Trail Making Test. Conclusions: These findings provide direct evidence that white matter tract disruption occurs in normal aging and would be consistent with the cortical disconnection hypothesis of age-related cognitive decline. Maximal changes in anterior white matter provide a plausible structural basis for selective loss of executive functions. In addition to providing new information about the biological basis of cognitive abilities, diffusion tensor MRI may be a sensitive tool for assessing interventions aimed at preventing cognitive decline. NEUROLOGY 2001;57:632–638 A progressive decline of cognitive functions is a rec- Indirect evidence for loss of functional “connectiv- ognized corollary of increasing age. Despite the clear ity” with age has been provided by a recent PET importance of these changes, the underlying mecha- study,5 where functional relationships between the nisms remain obscure. Early studies describing loss left dorsolateral prefrontal cortex and right hip- of neocortical neurons have been largely refuted by pocampus were examined during two cognitive tasks, the application of more accurate techniques.1 An- both activating a distributed processing network other possible mechanism is “cortical disconnection,” that included these nodes. In older subjects, both which leads to a loss of the functional integration of regions retained the capacity to become activated, neurocognitive networks. The concept of disconnec- but the functional relationships between them tion was first proposed by Geschwind in 19652 and changed with age, as did overall patterns of cognitive has gained credence as modern theories of cognitive activation. These findings suggest that age-related function have recognized the importance of large- decline in the performance of these tasks might re- scale, distributed cortical processing networks.3 More flect changes in functional integration rather than recently, coordinated activity of large distributed net- dysfunction of specific gray matter areas. works has been inferred from analysis of fMRI data.4 A plausible anatomic substrate for functional dis- From the Division of Clinical Neuroscience (Dr. O’Sullivan and Prof. Markus), St. George’s Hospital Medical School, London; and the Departments of Neuroimaging (Dr. Summers and Prof. Williams), Neuropsychology (Dr. Morris), and Old Age Psychiatry (Dr. Jones), Institute of Psychiatry, London, United Kingdom. Supported in part by the Stroke Association of the United Kingdom. Also supported by a Clinical Research Fellowship from St. George’s Hospital Medical School, United Kingdom (M.O’S.), by a grant from the Joint Research Committee of King’s College Hospital (P.E.S.), and by a grant from the Wellcome Trust (D.K.J.). Received November 13, 2000. Accepted in final form April 7, 2001. Address correspondence and reprint requests to Dr. Mike O’Sullivan, Department of Clinical Neuroscience, St. George’s Hospital Medical School, Cranmer Terrace, London SW17 0RE, United Kingdom; e-mail: [email protected] 632 Copyright © 2001 by AAN Enterprises, Inc. Figure 1. Fractional anisotropy images and selection of regions of interest (ROI). Images are shown at similar slice positions in a subject aged 71 years (left) and one aged 29 years (right). High signal intensity (bright- ness) reflects higher fractional aniso- tropy (FA). The genu and splenium of the corpus callosum can be seen clearly as areas of high anisotropy connecting the hemispheres. A whole white matter ROI is shown on the left image; ante- rior, middle, and posterior ROI are shown on the right image. Overall, sig- nal intensity in white matter is lower for the patient on the left, consistent with lower FA, and in turn lower tract integrity, in the older subject. connection is disruption of the white matter tracts search Ethics Committee of King’s College Hospital and all that link the components of distributed neurocogni- subjects gave informed, written consent. tive networks, or “structural disconnection.” A post- MRI. Diffusion tensor imaging was performed on a mortem study has provided evidence that normal 1.5-T G.E. Signa MR scanner (General Electric, Milwau- aging is accompanied by a loss of white matter fibers, kee, WI). An imaging sequence optimized for measurement particularly small, myelinated fibers.6 However, to of the diffusion tensor in white matter was used14 and the date, there has been no direct, in vivo demonstration of diffusion tensor elements calculated at each voxel. The structural disconnection in humans. diffusion tensor provides a three-dimensional representa- The recent development of diffusion tensor MRI tion of water diffusion. When diffusion is equal in all direc- has provided, for the first time, a noninvasive tions, it is described as isotropic, and when diffusion is method for delineating anatomy of white matter greater in some directions than others as anisotropic. FA can be considered as the proportion of the whole tensor pathways7 and subsequent assessment of pathologic that is anisotropic. Mean diffusivity is a directionally aver- tract disruption. In white matter tracts, water mo- aged measure of diffusion, with the effect of anisotropy tion is restricted by axonal membranes and myelin, removed. Measures of FA and mean diffusivity were de- and water moves more freely along the direction of a rived using equations previously published by Basser and tract than perpendicular to it. This directionality of Pierpaoli.15 The maximum strength of diffusion-encoding diffusion can be quantified by fractional anisotropy gradients was 22 mT·mϪ1. Fifteen to 18 near-axial slices (FA). FA varies from zero in tissue where diffusion is were obtained for each patient, providing near whole-brain equal in all directions to 1 where diffusion is entirely coverage. Diffusion tensor imaging took 4 to 6 minutes to unidirectional. Increasing anisotropy is a likely complete. Axial T1-weighted, T2-weighted, and fluid- marker of white matter tract integrity: anisotropy attenuated inversion recovery (FLAIR) images also were correlates with histologic markers of myelination,8 performed on all patients in the older group to exclude and there is accumulating evidence that changes in clinically silent brain disease. FA are of functional significance.9-13 Neuropsychological testing. Subjects in the older group In this study, we applied diffusion tensor MRI in a also underwent neuropsychological assessment. Two pa- group of elderly volunteers and younger subjects in tients in this group declined testing, so neuropsychological an attempt to provide a direct in vivo demonstration scores were available for 18 of the older group. Tests in- of white matter tract disruption with normal aging, cluded the Wisconsin Card Sorting Test, Reitan Trail Mak- and to correlate such changes with cognitive ing Test, Verbal Fluency, and the Mini-Mental State dysfunction. Examination. Premorbid intelligence was assessed using the National Adult Reading Test–Revised (NART-R) pro- Methods. Subjects. Twenty healthy elderly volunteers nunciation test. (age range, 56 to 85 years) were recruited from both a Image analysis. For each slice, a region of interest cohort of volunteers from the Clinical Age Research Unit (ROI) containing the white matter of one hemisphere was at King’s College Hospital and a separate cohort selected selected using a semiautomated approach (figure 1) using randomly from general practitioner lists in Bromley, South the Dispim display software (David Plummer, University London, United Kingdom. All were assessed by a clinician College London, United
Load more

Recommended publications
  • High-Yield Neuroanatomy
    LWBK110-3895G-FM[i-xviii].qxd 8/14/08 5:57 AM Page i Aptara Inc. High-Yield TM Neuroanatomy FOURTH EDITION LWBK110-3895G-FM[i-xviii].qxd 8/14/08 5:57 AM Page ii Aptara Inc. LWBK110-3895G-FM[i-xviii].qxd 8/14/08 5:57 AM Page iii Aptara Inc. High-Yield TM Neuroanatomy FOURTH EDITION James D. Fix, PhD Professor Emeritus of Anatomy Marshall University School of Medicine Huntington, West Virginia With Contributions by Jennifer K. Brueckner, PhD Associate Professor Assistant Dean for Student Affairs Department of Anatomy and Neurobiology University of Kentucky College of Medicine Lexington, Kentucky LWBK110-3895G-FM[i-xviii].qxd 8/14/08 5:57 AM Page iv Aptara Inc. Acquisitions Editor: Crystal Taylor Managing Editor: Kelley Squazzo Marketing Manager: Emilie Moyer Designer: Terry Mallon Compositor: Aptara Fourth Edition Copyright © 2009, 2005, 2000, 1995 Lippincott Williams & Wilkins, a Wolters Kluwer business. 351 West Camden Street 530 Walnut Street Baltimore, MD 21201 Philadelphia, PA 19106 Printed in the United States of America. All rights reserved. This book is protected by copyright. No part of this book may be reproduced or transmitted in any form or by any means, including as photocopies or scanned-in or other electronic copies, or utilized by any information storage and retrieval system without written permission from the copyright owner, except for brief quotations embodied in critical articles and reviews. Materials appearing in this book prepared by individuals as part of their official duties as U.S. government employees are not covered by the above-mentioned copyright. To request permission, please contact Lippincott Williams & Wilkins at 530 Walnut Street, Philadelphia, PA 19106, via email at [email protected], or via website at http://www.lww.com (products and services).
    [Show full text]
  • High-Yield Neuroanatomy, FOURTH EDITION
    LWBK110-3895G-FM[i-xviii].qxd 8/14/08 5:57 AM Page i Aptara Inc. High-Yield TM Neuroanatomy FOURTH EDITION LWBK110-3895G-FM[i-xviii].qxd 8/14/08 5:57 AM Page ii Aptara Inc. LWBK110-3895G-FM[i-xviii].qxd 8/14/08 5:57 AM Page iii Aptara Inc. High-Yield TM Neuroanatomy FOURTH EDITION James D. Fix, PhD Professor Emeritus of Anatomy Marshall University School of Medicine Huntington, West Virginia With Contributions by Jennifer K. Brueckner, PhD Associate Professor Assistant Dean for Student Affairs Department of Anatomy and Neurobiology University of Kentucky College of Medicine Lexington, Kentucky LWBK110-3895G-FM[i-xviii].qxd 8/14/08 5:57 AM Page iv Aptara Inc. Acquisitions Editor: Crystal Taylor Managing Editor: Kelley Squazzo Marketing Manager: Emilie Moyer Designer: Terry Mallon Compositor: Aptara Fourth Edition Copyright © 2009, 2005, 2000, 1995 Lippincott Williams & Wilkins, a Wolters Kluwer business. 351 West Camden Street 530 Walnut Street Baltimore, MD 21201 Philadelphia, PA 19106 Printed in the United States of America. All rights reserved. This book is protected by copyright. No part of this book may be reproduced or transmitted in any form or by any means, including as photocopies or scanned-in or other electronic copies, or utilized by any information storage and retrieval system without written permission from the copyright owner, except for brief quotations embodied in critical articles and reviews. Materials appearing in this book prepared by individuals as part of their official duties as U.S. government employees are not covered by the above-mentioned copyright. To request permission, please contact Lippincott Williams & Wilkins at 530 Walnut Street, Philadelphia, PA 19106, via email at [email protected], or via website at http://www.lww.com (products and services).
    [Show full text]
  • NEUROANATOMY Draw It to Know It This Page Intentionally Left Blank NEUROANATOMY Draw It to Know It
    NEUROANATOMY Draw It to Know It This page intentionally left blank NEUROANATOMY Draw It to Know It ADAM FISCH, MD Washington University in St. Louis School of Medicine Department of Neurology St. Louis, MO 1 2009 1 Oxford University Press, Inc., publishes works that further Oxford University’s objective of excellence in research, scholarship, and education. Oxford New York Auckland Cape Town Dar es Salaam Hong Kong Karachi Kuala Lumpur Madrid Melbourne Mexico City Nairobi New Delhi Shanghai Taipei Toronto With offices in Argentina Austria Brazil Chile Czech Republic France Greece Guatemala Hungary Italy Japan Poland Portugal Singapore South Korea Switzerland Thailand Turkey Ukraine Vietnam Copyright © 2009 by Adam Fisch. Published by Oxford University Press, Inc. 198 Madison Avenue, New York, New York 10016 www.oup.com Oxford is a registered trademark of Oxford University Press All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior permission of Oxford University Press. Library of Congress Cataloging-in-Publication Data Fisch, Adam. Neuroanatomy : draw it to know it / Adam Fisch. p. cm. Includes bibliographical references and index. ISBN 978-0-19-536994-6 1. Neuroanatomy—Graphic methods. I. Title. QM451.F57 2009 611.8—dc22 2008047543 9 8 7 6 5 4321 Printed in the United States of America on acid-free paper This book is dedicated in loving memory to my younger brother, David, whose humility and enthusiasm for learning remain a source of inspiration. This page intentionally left blank FOREWORD EUROANATOMY IS A nightmare for neuroimaging, the actual practice of neurology, most medical students.
    [Show full text]
  • Visual-Limbic Disconnection Syndrome of the Non-Human Primate with the Experimental Brain Lesion
    Nagoya ]. med. Sci. 31: 485-507, 1969 VISUAL-LIMBIC DISCONNECTION SYNDROME OF THE NON-HUMAN PRIMATE WITH THE EXPERIMENTAL BRAIN LESION - SOME ASPECTS OF THE KLUVER-BUCY'S SYNDROME WITH SPECIAL REFERENCE TO THE GNOSTIC ABILITY- Yun ANno 1st Department of Surgery, Nagoya University School of Medicine (Director: Prof Yoshio Hashimoto) ABSTRACT The adult male monkeys (macaca fuscata fuscata) were used in this study. After ecological behavioral observations on three selected pairs, bilateral temporal lobes of the dominant monkeys were removed and submissive ones were operated with only exploratory craniotomy for the control study. Subsequently, the behavioral changes were observed individually and in the each same pair. Indi­ vidual behavioral changes of the bilateral temporal lobectomized monkeys were those of the KHiver·Bucy's syndrome. Changes in pair suggested the "socio· agnostic" behavior. Selected one of the operated dominant monkeys with persistent Kliiver·Bucy's syndrome, psychometric examinations mediated visually, were performed to elucidate the mechanism of the agnostic behaviors which were observed ecolo­ gically, which was the main purpose of this study. The various visual discrimina· tions (of color, form, size and brightness) were tasked on the bilateral temporal lobectomized monkey under proper conditionings with comparison to the sham· operated monkey as the control monkey. Eventually, the bilateral temporal lobectomized monkey could not learn the tasks after even 200 trials each, while the control monkey was able to reach to the criterion (20 consecutive correct responses) finally. The essential factor of the agnostic behaviors seem to be settled on the dissociation of the limbic function from the visual function.
    [Show full text]
  • Corpus Callosum and Neglect Syndrome
    Published online: 2019-09-04 Review Article Corpus Callosum and Neglect Syndrome: Clinical Findings After Meningioma Removal and Anatomical Review David Gomes1, Madalena Fonseca1, Maria Garrotes1, Maria Rita Lima1, Marta Mendonça1, Mariana Pereira1, Miguel Lourenço1, Edson Oliveira1,2, José Pedro Lavrador1,2,3 1 Department of Anatomy, Two types of neglect are described: hemispatial and motivational neglect syndromes. Neglect Lisbon Medical School, syndrome is a neurophysiologic condition characterized by a malfunction in one hemisphere of 2 Department of the brain, resulting in contralateral hemispatial neglect in the absence of sensory loss and the Neurosurgical, Hospital right parietal lobe lesion being the most common anatomical site leading to it. In motivational Santa Maria, Centro neglect, the less emotional input is considered from the neglected side where anterior cingulate Hospitalar Lisboa Norte, cortex harbors the most frequent lesions. Nevertheless, there are reports of injuries in the corpus 3 ABSTRACT Lisboa, Portugal, Department callosum (CC) causing hemispatial neglect syndrome, particularly located in the splenium. of Paediatric and Adult It is essential for a neurosurgeon to recognize this clinical syndrome as it can be either a Neurosurgery, King’s College primary manifestation of neurosurgical pathology (tumor, vascular lesion) or as a postoperative Hospital NHS Foundation iatrogenic clinical finding. The authors report a postoperative hemispatial neglect syndrome after Trust, Denmark Hill, London a falcotentorial meningioma removal that recovered 10 months after surgery and performs a clinical, anatomical, and histological review centered in CC as key agent in neglect syndrome. Keywords: Corpus callosum, meningioma, neglect Introduction There are two hypotheses concerning the pathophysiology he right hemisphere is the dominant for the visuospatial of neglect.
    [Show full text]
  • The Disconnection Hypothesis.Pdf
    SCHIZOPHRENIA RESEARCH ELSEVIER Schizophrenia Research 30 (1998) 115-125 The disconnection hypothesis Karl J. Friston * The Wellcome Department of Cognitive Neurology, Institute of Neurology, Queen Square, London, WCI N 3BG, UK Received 3 June 1997; accepted 4 July 1997 Abstract This article reviews the disconnection hypothesis of schizophrenia and presents a mechanistic account of how dysfunctional integration among neuronal systems might arise. This neurobiological account is based on the central role played by neuronal plasticity in shaping the connections and the ensuing dynamics that underlie brain function. The particular hypothesis put forward here is that the pathophysiology of schizophrenia is expressed at the level of modulation of associative changes in synaptic efficacy; specifically the modulation of plasticity in those brain systems responsible for emotional learning and memory, in the post-natal period. This modulation is mediated by ascending neurotransmitter systems that: (i) have been implicated in schizophrenia; and (ii) are known to be involved in consolidating synaptic connections during learning. The proposed pathophysiology would translate, in functional terms, into a disruption of the reinforcement of adaptive behaviour that is consistent with the disintegrative aspects of schizophrenic neuropsychology. © 1998 Elsevier Science B.V. Keywords: Schizophrenia; Functional integration; Plasticity; Disconnection 1. Introduction for a pathology of integration. This paper is divided into three sections. In the first we address This article presents a disconnection hypothesis the two issues above. In the second section a and discusses it in relation to underlying neurobio- mechanistic version of the disconnection hypothe- logical mechanisms. Although disconnectionism sis is presented. The third section reviews evidence provides a compelling framework for understand- in favour of schizophrenia as a functional discon- ing schizophrenia it has to contend with two major nection syndrome.
    [Show full text]
  • Reversible Cerebral Vasoconstriction Syndrome Proton Beam Radiation Necrosis in Pediatric Patients Woven Endobridge Flow Disrupt
    AUGUST 2015 THE JOURNAL OF DIAGNOSTIC AND VOLUME 36 INTERVENTIONAL NEURORADIOLOGY NUMBER 8 WWW.AJNR.ORG Reversible cerebral vasoconstriction syndrome Proton beam radiation necrosis in pediatric patients Woven EndoBridge flow disrupter Official Journal ASNR • ASFNR • ASHNR • ASPNR • ASSR Engineered® by MicroVention HYDROGEL ADVANCED COILS ThT e cliniccalal benenefie ts of hydrogel NOW engginneeereed wiwitht the sooftf ness of bare plal titinunum onn the VV-Trak® Advd ana cec d Coill Systet m. INDICATIONS FOR USE: The HydroCoil® Embolic System (HES) is intended for the endovascular embolization of intracranial aneurysms and other neurovascular abnormalities such as arteriovenous malformations and arteriovenous fistulae. The HES is also intended for vascular occlusion of blood vessels within the neurovascular system to permanently obstruct blood flow to an aneurysm or other vascular malformation and for arterial and venous embolizations in the peripheral vasculature. The device should only be used by physicians who have undergone pre-clinical training in all aspects of HES procedures as prescribed by MicroVention. MICROVENTION, V-Trak, HydroCoil, HydroFrame, HydroFill and HydroSoft are registered trademarks of MicroVention, Inc. Scientific and clinical data related to this document are on file at MicroVention, Inc. Refer to Instructions for Use, contraindications and warnings for additional information. Federal (USA) law restricts this device for sale by or on the order of a physician. © 2015 MicroVention, Inc. 6/15 Frame, Fill, Finish HydroFrame® ® ® HydroCoil® Embolic System HydroCoil® Embolic System HydroCoil® Embolic System t $-*/*$"--: 456%*&% ):%30(&- t &''&$5*7&1,2,3 t &45"#-*4)&% 4"'&5: 130'*-&4 t 40'5&3 %&4*(/5 MicroVention, Inc. For more information or a product demonstration, Worldwide Headquarters PH +1.714.247.8000 contact your local MicroVention representative: 1311 Valencia Avenue Tustin, CA 92780 USA MicroVention UK Limited PH +44 (0) 191 258 6777 MicroVention Europe, S.A.R.L.
    [Show full text]
  • Self-Consciousness and “Split” Brains the Minds’ I
    OUP UNCORRECTED PROOF – REVISES, 04/09/2018, SPi Self-Consciousness and “Split” Brains The Minds’ I Elizabeth Schechter 1 Dictionary: NOSD 0003423032.INDD 3 4/9/2018 5:29:17 PM OUP UNCORRECTED PROOF – REVISES, 04/09/2018, SPi 3 Great Clarendon Street, Oxford, OX2 6D P, United Kingdom Oxford University Press is a department of the University of Oxford. It furthers the University’s objective of excellence in research, scholarship, and education by publishing worldwide. Oxford is a registered trade mark of Oxford University Press in the UK and in certain other countries © Elizabeth Schechter 2018 The moral rights of the author have been asserted First Edition published in 2018 Impression: 1 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, without the prior permission in writing of Oxford University Press, or as expressly permitted by law, by licence or under terms agreed with the appropriate reprographics rights organization. Enquiries concerning reproduction outside the scope of the above should be sent to the Rights Department, Oxford University Press, at the address above You must not circulate this work in any other form and you must impose this same condition on any acquirer Published in the United States of America by Oxford University Press 198 Madison Avenue, New York, NY 10016, United States of America British Library Cataloguing in Publication Data Data available Library of Congress Control Number: 2017961518 ISBN 978–0–19–880965–4 Printed and bound by CPI Group (UK) Ltd, Croydon, CR0 4YY Links to third party websites are provided by Oxford in good faith and for information only.
    [Show full text]
  • The Complex Structure of the Anterior White Commissure of the Human Brain
    *Manuscript Revised Final - Clean Click here to download Manuscript Revised Final - Clean: clean revised version of the Clickmanuscript.docx here to view linked References The Complex Structure of the Anterior White Commissure of the Human Brain: Fiber Dissection and Tractography Study Safiye Çavdar1, Ayşegül Esen Aydın2, Oktay Algin3,4, Seçkin Aydın5 1Koç University, School of Medicine, Department of Anatomy, Istanbul, Turkey. 2Bakırköy Ruh ve Sinir Hospital, Department of Neurosurgery, Istanbul, Turkey. 3Yıldırım Beyazıt University, Radiology Department, City Hospital, Ankara, Turkey and 4 National MR Research Center (UMRAM), Bilkent University, Ankara, Turkey 5Okmeydani Training and Research Hospital, University of Health Sciences, Department of Neurosurgery, Istanbul, Turkey. Address for correspondence Prof. Safiye Çavdar Koç University, School of Medicine, Department of Anatomy, 34450 Sarıyer Istanbul Turkey Fax No: 90 216 338 10 73 E-mail: [email protected] Funding: No funding was received for this study. Conflict of interest: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Ethical approval: All procedures performed in the studies involving human participants were approved by the ethical standards of the institutional Committee of Koç University. Informed consent: Informed consent was obtained from all individual participants for the DTI part of the study. The brains used for the fiber dissection was donated to the Anatomy department for education and research purposes. Key Words: Anterior commissure, commissural fibers, interconnection, fiber dissection, diffusion tensor tractography, human Abstract OBJECTIVES: Commissural fibers are necessary for bilateral integration, body coordination, and complex cognitive information flow between the hemispheres.
    [Show full text]
  • Visualizing the Neural Bases of a Disconnection Syndrome with Diffusion Tensor Imaging
    Visualizing the Neural Bases of a Disconnection Syndrome with Diffusion Tensor Imaging N. Molko1, L. Cohen1,2, J. F. Mangin3, F. Chochon2, S. Lehe´ricy 2, D. Le Bihan3, and S. Dehaene1 Downloaded from http://mitprc.silverchair.com/jocn/article-pdf/14/4/629/1757539/08989290260045864.pdf by guest on 18 May 2021 Abstract & Disconnection syndromes are often conceptualized exclu- hemifield words. Statistical analyses of diffusion images revealed sively within cognitive box-and-arrow diagrams unrelated to a damaged fiber tract linking the left ventral occipito-temporal brain anatomy. In a patient with alexia in his left visual field region to its right homolog across the lesioned area of corpus resulting from a posterior callosal lesion, we illustrate how callosum and stopping close to the areas found active in fMRI. diffusion tensor imaging can reveal the anatomical bases of a The behavioral disconnection syndrome could, thus, be related disconnection syndrome by tracking the degeneration of neural functionally to abnormal fMRI activations and anatomically to pathways and relating it to impaired fMRI activations and the absence of a connection between those activations. The behavior. Compared to controls, an abnormal pattern of brain present approach, based on the ‘‘negative tracking’’ of activity was observed in the patient during word reading, with a degenerated bundles, provides new perspectives on the under- lack of activation of the left visual word form area (VWFA) by left- standing of human brain connections and disconnections. & INTRODUCTION measured voxel. In particular, this anisotropy parameter The cognitive impairments that can be observed in has been shown to be highly sensitive to the degener- brain-lesioned patients are sometimes better explained ation of white matter tracts in brain-injured patients, in by a disconnection between two cerebral processes than whom focal decreases in anisotropy can be observed by primary damage to those processes themselves (Werring et al., 2000).
    [Show full text]
  • Frontal Collosal Disconnection
    cortex 48 (2012) 36e45 Available online at www.sciencedirect.com Journal homepage: www.elsevier.com/locate/cortex Special issue: Review Frontal callosal disconnection syndromes Giovanni Berlucchi a,b,* a National Institute of Neuroscience, Italy b Department of Neurological Sciences, Section of Physiology and Psychology, University of Verona, Italy article info abstract Article history: The interhemispheric connections of the cortical areas of the human brain are distributed Received 18 November 2010 within the corpus callosum according to a topographic order which is being studied in Reviewed 13 January 2011 detail by novel imaging techniques. Total section of the corpus callosum is followed by Revised 17 January 2011 a variety of interhemispheric disconnection symptoms each of which can be attributed to Accepted 18 April 2011 the interruption of fibers in a specific callosal sector. Disconnection symptoms deriving Published online 1 May 2011 from posterior callosal sections, disconnecting parietal, temporal and occipital lobes across the midline, are more apparent than those following anterior callosal sections dis- Keywords: connecting the frontal lobes. In spite of the massive bulk of the frontal callosal connections Corpus callosum in man, ascertained consequences of their interruption are limited to disorders of motor Frontal lobe control, with particular regard to bimanual coordination. Technical advances in brain Interhemispheric disconnection imaging and the design of appropriate tests are expected to reveal so far undetected Callosal topography deficits in the domain of executive and higher cognitive functions, resulting from callosal disconnection of the prefrontal cortices. ª 2011 Elsevier Srl. All rights reserved. 1. Interhemispheric disconnection damage, and the spared capabilities can thus be ascribed to syndromes and callosal maps the cortical regions with callosal connections spared by the damage (Gazzaniga, 2005).
    [Show full text]
  • The Role of White Matter Disconnection in the Symptoms Relating to the Anarchic Hand Syndrome: a Single Case Study
    brain sciences Case Report The Role of White Matter Disconnection in the Symptoms Relating to the Anarchic Hand Syndrome: A Single Case Study Valentina Pacella 1,2,3, Giuseppe Kenneth Ricciardi 4 , Silvia Bonadiman 5, Elisabetta Verzini 5, Federica Faraoni 1, Michele Scandola 1 and Valentina Moro 1,* 1 Npsy.Lab-VR, Dipartimento di Scienze Umane, Università di Verona, Lungadige Porta Vittoria, 17-37129 Verona, Italy; [email protected] (V.P.); [email protected] (F.F.); [email protected] (M.S.) 2 Brain Connectivity and Behaviour Laboratory, Sorbonne Universities, 75006 Paris, France 3 Groupe d’Imagerie Neurofonctionnelle, Institut des Maladies Neurodégénératives-UMR 5293, CNRS, CEA University of Bordeaux, 33076 Bordeaux, France 4 Neuroradiology, AOUVR Azienda Ospedaliera Universitaria Integrata di Verona, Piazzale Stefani, 1-37126 Verona, Italy; [email protected] 5 IRCSS, Ospedale Sacro Cuore-Don Calabria, Via Rizzardi, 4-37024 Negrar di Valpolicella, Italy; [email protected] (S.B.); [email protected] (E.V.) * Correspondence: [email protected]; Tel.: +39-45-8028370 Abstract: The anarchic hand syndrome refers to an inability to control the movements of one’s own hand, which acts as if it has a will of its own. The symptoms may differ depending on whether the brain lesion is anterior, posterior, callosal or subcortical, but the relative classifications are not conclusive. This study investigates the role of white matter disconnections in a patient whose Citation: Pacella, V.; Ricciardi, G.K.; Bonadiman, S.; Verzini, E.; Faraoni, F.; symptoms are inconsistent with the mapping of the lesion site. A repeated neuropsychological Scandola, M.; Moro, V.
    [Show full text]