Neuromotor Speech Impairment: It's All in the Talking

Abstract

The aim of this article is to explicate the uniqueness of the motor activity implied in spoken language production and to emphasize how important it is, from a theoretical and a clinical perspective, to consider the motor events associated with speaking as domain-specific, i.e., as pertaining to the domain of linguistic expression. First, phylogenetic data are reviewed demonstrating the specificity of the human vocal tract motor network regarding (i) the entrenchment of laryngeal motor skills within the organization of vocal tract movements, (ii) the evolution of a neural basis for skill acquisition within this system, and (iii) the integration of this system into an auditory-motor network. Second, ontogenetic evidence and existing knowledge about the experience-dependent plasticity of the brain are reported to explicate that during speech acquisition the vocal tract motor system is constrained by universal properties of speech production and by the specific phonological properties of the speaker's ambient language. Third, clinical data from dysarthria and apraxia of speech provide the background for a discussion about the theoretical underpinnings of domain-general versus domain-specific views of speech motor control. The article ends with a brief sketch of a holistic neurophonetic approach in experimental inquiries, assessment, and treatment of neuromotor speech impairment.

Acoustic variation during passage reading for speakers with dysarthria and healthy controls

“…One potential explanation for this would be that the speech acoustic characteristics were specific to the linguistic contexts of the three segments studied. A possible implication may pertain to the construct of “language-specific constraints”, as discussed by Ziegler and Ackermann (2013) (pp. 60).…”

Speech and nonspeech: What are we talking about?

“…2 Second, speech motor control is holistic and speech movements cannot be decomposed into component parts (“primitives”). This claim is reflected in Ziegler and Ackermann’s (2013) statement that ‘[…] vocal tract gestures in speaking […] can only be understood properly through their joint interaction in fabricating the sounds of syllables and words. From such a connectivist point of view, the constituents of a speech motor action can neither be isolated from their gestural context nor from their linguistic reference frame.’ (p. 62).…”

“…In recent years, there has been debate regarding the special status of speech among motor behaviours (Ballard, Robin, & Folkins, 2003; Bunton, 2008; Weismer, 2006; Ziegler, 2003a,b; Ziegler & Ackermann, 2013). Two main views in this debate are the task-dependent model (TDM; Ziegler, 2003a,b; Ziegler & Ackermann, 2013) and the integrative model (IM; Ballard et al, 2003) 1 .…”

“…Two main views in this debate are the task-dependent model (TDM; Ziegler, 2003a,b; Ziegler & Ackermann, 2013) and the integrative model (IM; Ballard et al, 2003) 1 . Briefly, the TDM proposes a specialised, distinct neuromotor control system dedicated to speech production, whereas other actions of the anatomical apparatus involved in speaking (e.g.…”

“…This paper will focus on two particular claims, versions of which have been eloquently laid out in recent years by various authors (Bunton, 2008; Weismer, 2006; Ziegler, 2003a,b; Ziegler & Ackermann, 2013). In particular, we will examine the claims that (1) speech is controlled by a specialised, distinct, dedicated neuromotor control system , and (2) speech is a holistic behaviour which cannot be decomposed into smaller parts .…”