Motor Speech Disorders:
characterizing phonetic speech planning and motor speech programming/execution and their impairments
In order to produce an utterance, a speaker has to transform an abstract linguistic message into a motor code, guiding the activity of more than 100 muscles involved in the process of articulation. Difficulties can affect motor stages of speech production, altering dramatically patients’ communication skills. These pathologies are known as Motor speech disorders (MSD) but this terms refers to a broad set of difficulties, depending on which and how different dimensions are impaired (articulation, speech rate, voice, prosody).
The aim of MoSpeeDi project is to reach a better understanding of the processes allowing the transformation of a linguistic message into articulated speech as well as the various manifestations of motor speech disorders. Indeed, the latest’ stages of speech production processes include the planning of invariant speech goals and their adaptation to the required contextual variations, the programming of motor programs and control of detailed neuromuscular commands to execute speech. However, the distinction and delimitation between phonetic speech planning and speech motor programming is still debated both from the theoretical and the clinical semiological perspectives. In particular, whereas most models posit distinct processes and different brain circuits for the planning of speech goals and subsequent processes of motor programming and execution, corresponding to different speech motor disorders (apraxia of speech versus dysarthria), the surface manifestations of impaired speech planning versus impaired speech programming/execution often overlap and the clinical differential diagnosis is far from being clear-cut.
The present project brings together a multidisciplinary consortium with complementary expertise in speech and language pathology, psycholinguistics, neurology, phonetics, and speech engineering in order to (a) improve the characterization of phonetic speech planning and motor speech programming, (b) identify acoustic, speech behavior and electrophysiological brain markers of these processes in a typically (unimpaired) functioning system and in MSD, with the overarching goal to (c) better isolate and classify speech alterations in MSD and differentiate those who derive from impaired speech planning from those deriving from impaired speech programming or execution. The originality of this project relies on the combination of psycholinguistic, phonetic, speech engineering and computational approaches to study speech in typical and impaired speakers. What makes this project particularly interesting and innovative is its fundamental, technological and clinical relevance.