Motor Speech Planning Versus Programming in Apraxia of Speech

EasyChair Preprint 6436

Abstract

The number of processes involved in the transformation of an abstract  linguistic code into articulated speech varies across models. Some authors propose a one-step model between phonological encoding and articulation (e.g. “phonetic encoding” in Levelt., 1989) while others  include two processes allowing the transformation of a linguistic code into a motor program (Guenther, 2016; Van der Merwe, 2020) sometimes called “motor speech planning” and “motor speech programming”. Apraxia of speech (AoS) involves impaired ability to retrieve and/or assemble the different elements of the phonetic plans (Blumstein, 1990; Code, 1998; Varley & Whiteside, 2001; Ziegler, 2008, 2009), and the impairment has been located at the motor speech planning processing stage. A different locus has been attributed to dysarthria, which underlying impairment has been located in the motor speech programming processing stage. There is however very limited empirical evidence in favor of two distinct processing stages transforming a linguistic (phonological) code into articulation. In the present study, we sought to target (a) motor speech planning via the comparison between the production of legal and illegal CCV clusters and (b) motor speech programming via the manipulation of uttering conditions. Four participants suffering from AoS following a left hemisphere stroke and four participants suffering from hypokinetic dysarthria (Parkinson’s disease – PD) participated in this study. They had to produce after a delay bisyllabic pseudo-words varying on the first syllable structure and legality (CV, legal CCV and illegal CCV).
The results showed an effect of uttering conditions with decreased performance in the whispering condition compared to normal speech only in the PD group and an effect of structure in both groups with an interaction showing larger effect in AoS. These results bring further support to models of speech production that propose two processing stages.

Keyphrases: Dysarthria, Motor speech planning, Motor speech programming, apraxia of speech

@booklet{EasyChair:6436,
  author    = {Marion Bourqui and Marina Laganaro},
  title     = {Motor Speech Planning Versus Programming in Apraxia of Speech},
  howpublished = {EasyChair Preprint 6436},
  year      = {EasyChair, 2021}}