Table Of ContentSantosh A. Helekar Editor
Animal Models
of Speech and
Language
Disorders
Animal Models of Speech and Language Disorders
Santosh A. Helekar
Editor
Animal Models of Speech
and Language Disorders
Editor
Santosh A. Helekar
Department of Neurology
and Neuroscience
The Methodist Hospital Research
Institute and Weill Medical
College of Cornell University
Houston , TX , USA
ISBN 978-1-4614-8399-1 ISBN 978-1-4614-8400-4 (eBook)
DOI 10.1007/978-1-4614-8400-4
Springer New York Heidelberg Dordrecht London
Library of Congress Control Number: 2013949275
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Pref ace
Dysfunction of motor, sensory, and cognitive aspects of speech and language forms
a substantial component of the clinical presentation in neurological practice. It is
frequently present in the most common neurological conditions such as stroke and
Parkinson’s disease, as well as many other neurodegenerative diseases, and neuro-
developmental conditions such as autism spectrum disorders. Primary speech and
language disorders also constitute a signifi cant burden to the well-being of our soci-
ety. For example, developmental stuttering affl icts more than 1 % of the population,
causing great emotional and social discomfort to people who suffer from it. There
is a great need to fi nd rational approaches to alleviate the suffering caused by all
these conditions. Toward this end, scientifi c research is focused on discovering their
underlying causal mechanisms in the brain. However, despite several decades of
sustained effort, we are no closer to understanding these mechanisms, as they per-
tain specifi cally to speech and language pathology.
Experience from other areas of biomedical research suggests that, arguably, an
important reason for this lack of progress is the perceived absence of elementary
animal models of speech and language pathologies or a reluctance to recognize
them. The latter circumstance results from the fact that speech and language have
long been thought to be unique attributes of the human species. Psychological and
neurological research in these areas has therefore been confi ned to human subjects
and patients. However, other frontiers of biomedical research have shown us that
animal models often pave the way to understanding a disorder at the causal and
mechanistic level and thereby enable researchers and physicians to devise rational
strategies toward therapy.
Basic research over the last 3 decades or so has uncovered similarities between
speech, especially its sensorimotor aspects, and vocal communication in several
nonhuman species. The most comprehensive studies so far have been conducted in
songbirds. Songbirds offer us a model system to study the interactions between
developmental or genetic predispositions and tutor-dependent infl uences, on the
learning of vocal communication. Songbird research has elucidated cellular and
molecular mechanisms underlying learning and production of vocal patterns,
v
vi Preface
auditory processing and perception of vocal sounds, vocal motor control, and vocal
neuromotor plasticity. More recently, the entire genome of the songbird zebra fi nch
has been sequenced. These discoveries, along with the identifi cation of several
genes implicated in familial human speech and language disorders, have made it
possible to look for analogues of speech and language dysfunction in zebra fi nches,
at least at the perceptual and sensorimotor levels. Two approaches in particular have
led us closer to the development of animal models of human speech conditions,
namely, developmental stuttering and a familial verbal dyspraxia associated with a
mutation in the gene for the transcription factor FoxP2.
Work on other animals that show developmental sensorimotor learning of vocal
sounds used for communication has also shown signifi cant progress, leading to the
possibility of development of models of speech and language dysfunction in them.
In nonhuman primates, while vocal learning per se is not very prominent, investiga-
tions on their communicative abilities have thrown some light on the rudiments of
language. As far as auditory processing is concerned, echolocation in bats has long
served as a rich source of fundamental insights.
There is a great need for a synthesis of all observations and ideas that have emerged
from basic and clinical research into the neuroscience of vocalization and auditory pro-
cessing, in order to develop a rational animal model-based framework for understanding
and management of speech and language pathologies. The ultimate goal of satisfying
this need makes the publication of this book focused on animal models of speech and
language disorders, detailing the overall investigative approach of neurobehavioral
studies in animals capable of vocal communication and learned vocalizations, a much-
needed and worthwhile project. This book is arguably the fi rst of its kind. I believe it
serves as a unifying review of research in a new multidisciplinary frontier, spanning the
molecular to the behavioral, for clinicians and researchers, as well as a teaching resource
for advanced speech pathology and neuroscience students.
The book covers a wide range of disciplines related to speech and language and
vocal communication in animals. In Part I, the fi rst chapter deals with the current
state of understanding of the neurology of speech and language in terms of brain
substrates, representation, and theoretical models. The second chapter is a review of
what is known about the genetics of speech and language disorders with special
emphasis of the FoxP2 gene mutations, on which there is the most amount of new
information. In Part II, Chap. 3 introduces and discusses the behavioral and physi-
ological aspects of the songbird model of vocal learning. It focuses on developmen-
tal time scales of changes in vocal sounds and sequences of sound, as well as motor
control and the role of sleep in these processes. The auditory pathway for encoding
and processing of vocal signals is discussed in Chap. 4 . Chapter 5 describes the fi nd-
ings of the zebra fi nch genome research and its application to molecular biological
studies on song learning. The latter task has been extended in Chap. 6 to include
current and prospective ways to elucidate detailed molecular mechanisms with
translational signifi cance. Chapter 7 wraps up the section on songbird neurobiology
by proposing an elementary birdsong-based model of stuttered speech in zebra
fi nches and discusses the possible involvement of perceptual and synaptic plasticity
and neuromodulatory infl uences in the underlying mechanisms.
Preface vii
The last section is concerned with vocal signaling in three different groups of
mammals that have contributed substantially to our understanding of neurophysio-
logical and/or cognitive aspects of social communication. In Chap. 8 the authors
present a compilation of fi ndings on the rich variety of calls used by bats for com-
munication and echolocation and the manner in which they are processed at the
neuronal level. Chapter 9 concentrates on social communication in New World
monkeys and the extent to which the study of their complexity and cognitive role
contributes to gleaning insights into the rudiments of grammar and meaning of
vocal sounds. The fi nal chapter is an examination of the accumulated knowledge on
gestures and socially signifi cant sounds produced by our closest evolutionary ances-
tors, the great apes, in terms of their relevance to evolution of speech and language
and their shared brain substrates in man and ape.
I am fortunate to have an illustrious panel of experts graciously agree to write
chapters on their respective areas of research and teaching for this book. I am deeply
grateful to them for their painstaking efforts, as well as to other experts who have
reviewed their chapters and offered valuable suggestions to make them better. This
book would not have been possible without the kind assistance, guidance, and hard
work of Melissa Higgs and Elektra McDermott of Springer. I hope the readers will
fi nd this joint endeavor of ours useful and informative.
Houston, TX, USA Santosh A. Helekar
Contents
Part I Introduction to Speech and Language Disorders
1 Neurology of Speech and Language ..................................................... 3
David B. Rosenfi eld
2 Genetic Pathways Implicated in Speech and Language ..................... 13
Sonja C. Vernes and Simon E. Fisher
Part II Songbird Model of Vocal Learning
3 Time Scales of Vocal Learning in Songbirds ....................................... 43
Ofer Tchernichovski and Daniel Margoliash
4 The Songbird Auditory System ............................................................. 61
Sarah M. N. Woolley
5 Prospective: How the Zebra Finch Genome
Strengthens Brain-Behavior Connections in Songbird Models
of Learned Vocalization ......................................................................... 89
Sarah E. London
6 The Molecular Convergence of Birdsong and Speech ........................ 109
Mugdha Deshpande and Thierry J. Lints
7 Stuttered Birdsong ................................................................................. 185
Santosh A. Helekar, Delanthi Salgado-Commissariat,
David B. Rosenfi eld, and Henning U. Voss
ix
