Learning Disabilities and Brain Function: A Neuropsychological Approach

618 Pages·1994·12.431 MB·English

by  William H. Gaddes, Dorothy Edgell (auth.)

Learning Disabilities and Brain Function
A Neuropsychological Approach
Third Edition
To the children and adults seen clinically at the
Neuropsychology Laboratory of the University of Victoria for
the past thirty years, and the many children assessed and
treated at the Queen Alexandra Centre for Children's Health
over the past decade, with sincere gratitude. They have been
our most valuable teachers.
William H. Gaddes Dorothy Edgell
Learning Disabilities
and Brain Function
A Neuropsychological Approach
Third Edition
With a Foreword by George W. Hynd
With 53 Figures
Springer Science+Business Media, LLC
William H. Gaddes Dorothy Edgell
Professor Emeritus Clinical Child Neuropsychologist
Department of Psychology Queen Alexandra Centre for Children's Health
University of Victoria Adjunct Assistant Professor
Victoria, British Columbia Department of Psychology
Canada V8W 2Y2 University of Victoria
Victoria, British Columbia
Canada V8W 2Y2
Graphic design on cover by William D. West
Library of Congress Cataloging-in-Publication Data
Gaddes, William H.
Learning disabilities and brain function : a neuropsychologicaJ
approach I William H. Gaddes, Dorothy EdgeIl. - 3rd ed.
p. cm.
Includes bibliographicaJ references and index.
ISBN 978-1-4419-2832-0 ISBN 978-1-4757-2255-0 (eBook)
DOI 10.1007/978-1-4757-2255-0
1. Learning disabilities. 2. Learning-PhysiologicaJ aspects.
3. Neuropsychology. 1. EdgeIl, Dorothy. II. TitIe.
[DNLM: 1. Learning Disorders-physiopathology.
2. Neuropsychology. WS 110 G123L 1993]
RJ496.L4G33 1993
618. '85889-dc20
DNLM/DLC 93-28185
Printed on acid-free paper.
© 1994 Springer Science+Business Media New York
Originally published by Springer-Verlag New York, Inc. in 1994
Softcover reprint ofthe hardcover 3rdedition 1994
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9 8 765 4 3 2 1
ISBN 978-1-4419-2832-0
Prelude
And now, I said, let me show in a figure how far our nature is enlightened or
unenlightened: Behold! Human beings living in an underground den, which has a
mouth open towards the light and reaching all along the den; here they have been
from their childhood, and have their legs and necks chained so that they cannot
move, and can only see before them; being prevented by the chains from turning
round their heads. Above and behind them a fire is blazing at a distance, and
between the fire and the prisoners there is a raised way; and you will see, if you
look, a low wall built along the way, like the screen which marionette players have
in front of them, over which they show the puppets ....
Like ourselves, I replied; and they see only their own shadows, or the shadows
of one another, which the fire throws on the opposite wall of the cave.
Plato, The Republic, Book VII
Modern psychology takes completely for granted that behavior and neural function
are perfectly correlated, that one is completely caused by the other. ... One cannot
logically be a determinist in physics and chemistry and biology, and a mystic in
psychology.
D.O. Hebb (1949)
Foreword to the Third Edition
Now in its third edition, this time coauthored with Dr. Dorothy
Edgell, Learning Disabilities and Brain Function has clearly be
come a classic text. Rarely do I visit colleagues who do not have a
copy in their professional libraries. There are a variety of reasons
why this particular volume has been so widely and enthusiastically
received. I suspect, however, that the primary reason is that Dr.
Gaddes, in the previous editions, achieved exactly what he intended
to accomplish despite well-intended advice to pursue other, more
modest goals in preparing a text on the presumed relationship
between learning disabilities and neurological function.
In the preface to the first edition, Dr. Gaddes stated his goal to
prepare a book that would be of interest to both neuropsychologists
and educators. He was warned that it would be impossible to write
such a book, because of the potential risk associated with over
simplification for those with little background in brain-behavior
relations. At the same time, confusion might result from trying to
adequately integrate the vast and often conflicting literature on the
neuropsychological basis of learning disabilities. Drs. Gaddes and
Edgell, however, have accomplished what many would have hesi
tated to attempt. They have produced a comprehensive volume
that precisely addresses the relationship between brain function and
the behavioral manifestations associated with learning disabilities.
Despite those who would attempt to enforce their belief that the
study of behavior can be divorced from the study of its neurological
origins, the study of behavior necessarily is the study of the brain.
The behavior we observe is obviously the end product of the
integrated functioning of the central nervous system. With regard
to learning disabilities, a careful reading of the seminal reports of
Dejerine, Hinshelwood, Bastian, and other investigators at the
turn of this century reveals evidence in support of the genetic and
neurological bases of the behaviors we clinically characterize as
manifestations of learning disabilities. The clinical reports included
in this volume provide a meaningful understanding that best ex
emplifies the research reported in this book. And it is in this
manner that psychologists, educators, and other clinicians will find
the contents their of this volume not only readable, but articulate
in presentation.
Foreword to the Third Edition
Vll
Although the study of individuals with learning disabilities has
continued for well over a century, only within the past several
decades have learning disabilities been formally acknowledged
through laws and regulations that require the provision of services
to those who experience severe difficulties in learning. In ad
dition to national definitions and state or provincial regulations re
garding the diagnosis and treatment of learning disabilities, various
nosologies now include definitions and diagnostic criteria. Further,
the presumed neurological basis of learning disabilities has received
considerable attention from clinicians and researchers. In large
part, this increased interest has been sustained and fostered by
research methodologies not previously available. Only in the past
two decades have postmortem, neuroimaging, and sophisticated
neuropsychological procedures been available to study brain
behavior relationships in individuals with learning disabilities.
These research endeavors have been wonderfully productive in
providing evidence that the brains of learning disabled persons
may be morphologically and functionally different than those of
normal controls. Importantly, evidence now suggests that people
with acquired and developmental learning disabilities may indeed
share a disruption of the same neurological systems. In other
words, whether of developmental or acquired origin, learning dis
abilities result from a disruption of known systems in the brain.
Although the etiology may be different in each case, the behavioral
symptomatology observed is consistent with our rapidly evolving
understanding of brain-behavior relations. This is why this volume
is so important. Drs. Gaddes and Edgell approach this literature
not only from the point of our theoretical understanding of brain
behavior relations, but they provide a meaningful integration of
this literature with our clinical and educational experience. Simply
put, they have successfully taken on the normously difficult task of
showing how our understanding of the central nervous system
supports and extends our ability to effectively identify and work
with persons who have learning disabilities.
To accomplish this task, they have had to carefully present
research from neurology, psychiatry, psychology, and education in
a way that provides a unified conceptualization of learning dis
abilities. Of course this is appropriate as the most recent definition
of neuropsychology acknowledges the multidisciplinary nature of
the field. That is why this volume has been so widely received
and cited-it is a theoretically consistent and multidisciplinary
presentation of a complex literature in a concise and clinically
relevant format.
Further, this volume provides new and updated information
on comorbid disorders that may be observed in individuals with
viii Foreword to the Third Edition
learning disabilities. As an example, this volume now includes a
fine chapter on "Attention Deficit Disorder," prepared by Dr.
Edgell. Research conducted over the past several decades has
produced a rapidly evolving literature not only on the deficits in
attention that many persons with learning disabilities experience,
but on the presence of comorbid disorders that may accompany
learning disabilities. Understanding the complexities in arriving at
a diagnosis of attention deficit disorder and its possible relationship
to learning disabilities is important in providing appropriate psy
chological, educational, and medical treatment. In this regard, this
edition is indeed new and improved.
Significant challenges exist on our horizon. Educators must be
vigilant that the recent move toward inclusion of special education
students within regular classroom settings does not adversely impact
on the provision of relevant and quality services to these pupils.
Psychologists must address the need for more accurate and relevant
diagnostic procedures aimed at providing information that can be
translated into documented treatment procedures that are effective
and targeted at all of the educational and emotional needs of these
individuals. Neurologists must continue their efforts to interface
with the educational process by becoming more involved in moni
toring medical treatment required by some learning disabled stu
dents. Finally, researchers must effectively present their findings to
the broad range of professionals who may most profit from them.
The information provided in this volume by Drs. Gaddes and
Edgell make a great stride forward in this larger context.
It has been an honor to provide this Foreword. Little did I sus
pect that when Dr. Gaddes and I first corresponded two decades
ago that I would be asked to prepare these comments. His early
writings had a very significant impact on my own understanding
of learning disabilities. I am sure that this volume will likewise
influence those who seek to understand brain-behavior relations in
persons with learning disabilities. This volume is a landmark in the
literature on learning disabilities and consequently commands our
incorporating the knowledge shared herein in our daily experience.
George W. Hynd, Ph.D.
University of Georgia
Foreword to the Second Edition
Reading this volume, chapter by chapter, I had a feeling of exu
berance and exhiliration. It is both a privilege and a challenge to
write a foreword for this second edition of Learning Disabilities and
Brain Function. The scope and quality of the scientific and clinical
insights expressed are unusual. It is difficult to do justice to the
book within the constraints of a foreword. I can only reflect its sig
nificance to instructors, scientists, and clinicians in education, psy
chology; psychiatry, pediatrics, speech pathology and neurology.
In the early chapters there are discussions of brain function as it
relates to learning and learning disabilities, with many implications
for better understanding of the neurology of behavior. These
chapters are followed by an articulate consideration of neuropsy
chological disorders, definition, identification and diagnosis of the
cognitive dysfunctions that underlie learning disabilities. There is
an analysis of the role of perception, as well as of the significance
of impared sensory and motor-cognitive processes. The concluding
chapters comprise a clear, erudite, yet practical discourse on the
spectrum of language disorders, including the spoken, read, and
written forms. Dr. Gaddes provides a constructive review of what
it means when children have aphasia, of how this language dis
order has implications for other types of learning. He elucidates
and evaluates the status of our knowledge relative to childhood
dyslexia and dysgraphia. This analysis holds promise for clarifi
cation of the issues that have been disconcerting, especially to
educators and psychologists.
Dr. Gaddes adheres to the scientific evidence but in so doing he
reveals the various ways in which carefully programmed remedi
ation can benefit many children throughout the school years. I
found this emphasis especially noteworthy for special educators
and for regular teachers as well. Because of his wide experience as
an educator and neuropsychologist, Dr. Gaddes does not simply
present scientific evidence and overlook the pressing problems
confronting those who are responsible for evaluating and teaching
children who have learning disabilities. He presents evidence with
a frame of reference, a point of view, that recognizes the urgency
of being able to remediate and alleviate the total complex of
x Foreword to the Second Edition
circumstances that surround children, educationally and socially.
He urges that all who are involved share knowledge so that these
children can be better understood, their well-being fostered more
effectively, and the confusions that commonly are associated with
them be relieved. And if we professionals do not interact and share
knowledge, the result will be less, not better services for the
children we serve.
In studying this volume one cannot but be mindful of the ways
that the learning-disability concept has prevailed upon other fields
which focus on children. As manifested by this volume, this concept
has significantly influenced education. It has enhanced and fostered
special education, as can be observed in any school. Less obvious
is the fact and the manner in which it has penetrated general
education. There is a movement toward greater awareness of indi
vidual differences and needs, of how patterns of learning differ,
verbally and nonverbally. Moreover, learning itself as a manifes
tation of cognitive behavior, and its role in the acquisition of
meaning has taken on new significance. This volume, through its
interdisciplinary contributions, broadens this salient new emphasis
in our schools and in society.
Perhaps we can see an even greater impact of the learning
disability concept in the fields of psychology, psychiatry and neuro
logy. Neuropsychology now is one of the prominent branches of
psychology. But the construct that cognitive dysfunctions result in
disturbed learning processes has been recognized by other spe
cialties in psychology. The division of clinical child psychology has
presented monographs that are important contributions. Pediatric
and school psychology are both heavily involved in meeting the
needs of children with psychoneurological cognitive disturbances.
Psychologists working in these specialty areas will find that this
volume has many observations and suggestions that bear directly
on the ways children with learning disabilities can be evaluated and
helped through programs designed specifically for the dysfunctions
defined through careful, systematic, objective analysis of the im
positions on learning.
This volume, the theme of which is cognitive functions as they
relate to the neurology of learning, is relevant and purposeful also
in other respects. As the science of learning disabilities develops, it
might be that its most consequential influence will be in cognitive
psychology. The concept of learning disabilities itself is based pri
marily on constructs evolved by cognitive psychologists during the
past several decades. Many scientists agree that the most funda
mental behavioral manifestation of a learning disability is the dys
function of otherwise normal cognitive processes. Throughout this
volume an underlying theme is that this construct must not be
overlooked. Rather, the emphasis is that this basic character of