30 ans de recherches en phonétique clinique au LPL

The research in Clinical Phonetics aims to improve our knowledge of speech pathologies by comparing phonetic methods and research with clinical data and clinicians’ diagnoses. In France, Clinical Phonetics has developed over the last thirty years bringing together phoneticians, linguists, computer scientists, engineers, physicians, speech therapists and clinicians.The “Laboratoire Parole et Langage” (LPL) has a long experience in this field through many collaborations with local hospitals and other partners at the national level. These collaborations have led to the development of several projects dealing with a wide variety of pathologies (dysphonia, Parkinson’s disease, ALS, multiple sclerosis, cancers of the oral cavity and oropharynx, apraxia, etc.). Traditional phonetic methodologies (analysis of speech production and perception) have been adapted to the specific constraints of pathological speech. In particular, the LPL has strongly questioned and improved aerophonometry, speech intelligibility measurements, transcription of pathological speech, and acoustic analysis.There are many research questions in clinical phonetics, but they can be structured around two main axis: (1) what are the contributions of phonetics research to the assessment of speech pathologies?; (2) how can speech pathologies deepen our understanding of the complex mechanisms underlying speech production and perception? The goal of this work is twofold: first, to assist clinicians in the evaluation of the severity of a disorder, either for a punctual assessment or in a therapeutic evaluation (rehabilitation, surgical, pharmacological, electrophysiological treatment); secondly, to improve our knowledge on speech by characterizing the productions considered as “atypical”.Without being exhaustive, this chapter offers an overview of research in clinical phonetics at the LPL. After a brief history recalling the emergence of clinical phonetics at the LPL, we organized the chapter around the current work carried out at the LPL on laryngeal pathologies, motor disturbances, speech intelligibility and speech planning disorders.The first studies at LPL combining phonetics and clinical studies date back to the mid-1970s–1980s. These studies became a research focus at the LPL in the 1990s, thanks to formal collaborations with the ENT department of the Timone University Hospital in Marseilles. At that time, the main research interest for the ENT department was voice disorders analysis. This first research has continued to develop and the field of investigation has been extended to speech disorders, particularly those of neurological origin, such as motor or speech planning disorders, in which collaborations with the neurology department of the Pays d’Aix Hospital have been decisive. These clinical collaborations have also supported the valorization and dissemination of this research in the socio-economic world, in particular with the invention, manufacture and marketing of the Assisted Voice Evaluation (EVA) device.Laryngeal pathologies were the first area explored and have led to many publications. The establishment of vocal assessment, both at perceptual and instrumental level, has monopolized most of the efforts. Nevertheless, and in spite of the contribution of automatic speech processing, the instrumental approach derived from phonetics remains little applied in clinical practice for various reasons discussed in the chapter. Some perspectives are proposed and may open new horizons for clinical phonetics. Laryngeal pathologies have also addressed questions to the linguistic functioning and the phonological representation of language units, in particular with regard to the voicing feature, which is the basis of a basic and almost universal lexical contrast in the languages of the world.Motor disturbances whose symptoms on speech are grouped under the term dysarthria have also been the object of important studies at the laboratory, particularly in the context of Parkinson’s disease. These studies have contributed to the pathophysiological model of the disease by measuring various parameters of speech in the context of monitoring the disease. For example, the therapeutic effects (drug or electrophysiological) were studied via acoustic and physiological (aerodynamic) instrumental analyses. The prosodic dimension was also given an important place. This work has allowed us to highlight the characteristics of the speech of Parkinson’s patients by integrating the interactions between the pathological disorders and the linguistic structure at different levels of organization.The measurement of speech intelligibility, which is a recurrent theme in the laboratory’s research, as developed strongly and has been integrated into a clinical perspective, first with the work on Parkinson’s disease, then in the context of the after-effects of cancers of the oral cavity and oropharynx. Biases related to speech perception have led to various alternatives to intelligibility test batteries allowing to propose linguistically justified solutions adapted to clinical practice. They have also made it possible to study more precisely the articulation between the various perceptual levels involved in decoding and understanding speech.More recently, questions about the planning of speech production have emerged in the laboratory. Speech pathology and clinical phonetics provide a framework for testing these questions. Research comparing healthy subjects vs. those with cognitive deficits related to multiple sclerosis is being conducted at LPL to explore how cognitive constraints influence speech parameters of planning. Finally, we think that an epistemological and multidisciplinary challenge is now facing clinical phonetics. Clinicians and phoneticians have learned to research and work together on complex problems that have a fundamental research issue but also a societal and public health issue. The challenge is therefore to promote interaction and understanding of the issues that move these two communities. Phoneticians must be able to propose fields of application of their knowledge adapted to the real and practical problems of clinicians; and conversely, clinicians must be able to better propose observations that question and nourish reflections on the models of production, perception and understanding of speech and language.