Effect of boost articulation therapy (BArT) on intelligibility in adults with dysarthria.

BACKGROUND: The articulatory accuracy of patients with dysarthria is one of the most affected speech dimensions with a high impact on speech intelligibility. Behavioural treatments of articulation can either involve direct or indirect approaches. The latter have been thoroughly investigated and are generally appreciated for their almost immediate effects on articulation and intelligibility. The number of studies on (short-term) direct articulation therapy is limited. AIMS: To investigate the effects of short-term, boost articulation therapy (BArT) on speech intelligibility in patients with chronic or progressive dysarthria and the effect of severity of dysarthria on the outcome. METHODS & PROCEDURES: The study consists of a two-group pre-/post-test design to assess speech intelligibility at phoneme and sentence level and during spontaneous speech, automatic speech and reading a phonetically balanced text. A total of 17 subjects with mild to severe dysarthria participated in the study and were randomly assigned to either a patient-tailored, intensive articulatory drill programme or an intensive minimal pair training. Both training programmes were based on the principles of motor learning. Each training programme consisted of five sessions of 45 min completed within one week. OUTCOMES & RESULTS: Following treatment, a statistically significant increase of mean group intelligibility was shown at phoneme and sentence level, and in automatic sequences. This was supported by an acoustic analysis that revealed a reduction in formant centralization ratio. Within specific groups of severity, large and moderate positive effect sizes with Cohen's d were demonstrated. CONCLUSIONS & IMPLICATIONS: BArT successfully improves speech intelligibility in patients with chronic or progressive dysarthria at different levels of the impairment. What this paper adds What is already known on the subject Behavioural treatment of articulation in patients with dysarthria mainly involves indirect strategies, which have shown positive effects on speech intelligibility. However, there is limited evidence on the short-term effects of direct articulation therapy at the segmental level of speech. This study investigates the effectiveness of BArT on speech intelligibility in patients with chronic or progressive dysarthria at all severity levels. What this paper adds to existing knowledge The intensive and direct articulatory therapy programmes developed and applied in this study intend to reduce the impairment instead of compensating it. This approach results in a significant improvement of speech intelligibility at different dysarthria severity levels in a short period of time while contributing to exploit and develop all available residual motor skills in persons with dysarthria. What are the potential or actual clinical implications of this work? The improvements in intelligibility demonstrate the effectiveness of a BArT at the segmental level of speech. This makes it to be considered a suitable approach in the treatment of patients with chronic or progressive dysarthria.

Intelligibility as a linear combination of dimensions in dysarthric speech.

UNLABELLED: Speech samples of 79 dysarthric patients (native speakers of English) were judged by two experienced judges by means of a perceptual rating scale covering the four main dimensions of speech production: voice quality, articulation, nasality and prosody as well as overall intelligibility. In order to determine the relative influence of the four basic dimensions on intelligibility in this study group, a multiple regression model was applied. This model shows that intelligibility can be expressed as a linear combination of weighted perceptual dimensions (R2 = 0.89). This expression reveals the relative importance of the individual dimensions on overall intelligibility. Articulation is shown to be the strongest contributor to intelligibility. A group of 16 dysarthric patients (native speakers of Dutch) was used as a control group in order to evaluate the validity of the expression. Judged and calculated ratings (within the 95% prediction intervals) were in agreement for 75% of the patients. These findings may contribute in the construction of a better balanced measure of functional intelligibility. LEARNING OUTCOMES: 2. The impact of articulation on intelligibility is dominant but inclusion of the dimensions "nasality", "voice" and "prosody" results in a more balanced estimation of intelligibility.