Introduction

Nick Miller and Anja Lowit

What is This Book All About?

This book is about motor speech disorders (MSDs), about aspects of their assessment and treatment, about understanding the underlying neurophysiological and neuropsychological disruptions that bring about disorders of speech motor control. More precisely, the book is about what we can find out about these disorders from a particular perspective – cross-language studies.

MSDs are a cover term for problems with voice production/phonation and articulation due to neurological damage that impairs the planning and execution of movements required to produce speech (we offer an introduction to the field later for those not familiar with it). Disruption may affect one or more of the processes and actions underlying speech production, for example dysfunction in the 'selection' of the sounds required to say a word, problems in the planning of the movements needed to produce those sounds. Disruption may alter the transmission of nerve impulses between parts of the brain involved in executing the planned movements, cause difficulties with transmission of these impulses between the brain and other parts of the central nervous system and/or problems with relaying the impulses out via the peripheral nervous system to the muscles involved in articulation. The muscles active in speech output range from the diaphragm and thorax involved in the control of in- and expiration, via the larynx for phonation and the velum for regulating the degree of nasality, to the tongue, lips and mandible. These disruptions may affect any or all of breathing, phonation, resonance and articulation and in turn the ability to produce a voice loud and clear enough to be heard, articulation precise enough to deliver intelligible speech and variations in stress and intonation patterns necessary to convey suprasegmental aspects of meaning for the language a person speaks.

There are countless tomes and myriad articles written on MSDs, and so we already know a great deal about them. But, there is one big proviso to most of what we have to say – what we know about MSDs, how to recognise them, how people classify them, their differential diagnosis and many of the clinical practices around their assessment and treatment, rest predominantly on studies of speakers of English (and within those mainly American speakers) and structurally and phonologically closely related Indo-European languages. Such a narrow perspective in the field of communication always runs the risk of producing theories and practices that may not be universally applicable and may even be wrong when applied beyond the narrow confines of the linguistic and social contexts in which they were developed. This provides the rationale for this book.

Studies of MSDs do exist in other languages, most notably Chinese, German, French and Japanese (see chapters later in the book). A cross-language dimension, though, has been largely lacking, especially when it has come to the development of theories around speech motor control and its breakdown, though studies of deaf sign language users who have different neurological conditions do provide a marked exception here, as elucidated in a later chapter. This book aims to redress some of that imbalance. It contains two sections. The first part provides an introduction to MSDs and related areas in a cross-language context. The first three chapters set the scene, defining what we mean by cross-language studies, providing background information on MSDs for those who are not that familiar with this group of communication impairments, and discussing the fundamentals of assessing and treating MSD in a cross-language context. These chapters are followed by selected topics that demonstrate the progress made in the understanding of MSDs and related areas from cross-language studies and the kinds of issues that need to be considered in further investigations in this area. The second half of the book gathers overviews from a range of languages around the world. Each chapter contains a summary of the segmental and suprasegmental features of the language that set it apart from English, and discusses assessments and treatment programmes that have been developed for this medium. In addition, they offer a flavour of the status of knowledge on MSDs in those languages and begin to look at the nature of similarities and differences between languages or types of language that could form the basis of future cross-language investigations to advance our understanding of MSDs and speech motor control in general.

There is one more dimension implicit in this book. Another angle from which researchers have viewed communication to gain insights into brain–language relationships, clues to how language and sound processing reflect neurological processing, has been the study of speech and language breakdown, whether in developmental disorders or in acquired disorders of language and speech after stroke, head injury or in other neurological conditions. By examining what breaks down, and in what ways, in association with lesions in which...