|
Article Excerpt
This study was designed to investigate the effect of intensive voice reatment (Lee Silverman Voice Treatment [R]) on formant steadiness in 10 speakers with hypokinetic dysarthria associated with idiopathic Parkinson's disease and parkinsonian syndromes. Digital acoustic analysis was used to measure the variability of formant frequencies around their means across sustained vowel phonation. This technique was previously used to demonstrate reduced formant steadiness in speakers with movement disorders including Parkinson's disease. One hundred eighty productions of "ah" were examined yielding coefficients of variation for the formant frequencies of each vowel production. Statistical analysis demonstrated a significant main effect of treatment (p < .05) wherein variability associated with the first and second formants (F1, F2) decreased following treatment. The results of this study suggest that increasing vocal effort/intensity also improves formant steadiness.
**********
Parkinson's disease is a neurodegenerative condition that can have a devastating impact on many areas, including an individual's motor skills, swallowing, and speech. It affects 1 in 100 people over the age of 60 (National Parkinson Foundation, 2007). Hypokinetic dysarthria associated with idiopathic Parkinson's disease causes reduced intelligibility resulting from decreased loudness, monopitch, monoloudness, imprecise articulation, and disordered speaking rate (Darley, Aronson, & Brown, 1969a, 1969b). Regardless of the type, dysarthric speakers typically exhibit some degree of reduced motor control (Gerratt, 1983). Given the three cardinal signs of Parkinson's disease (bradykinesia, tremor, and rigidity), individuals are often unable to maintain adequate postural stability. Most research is focused in postural stability and motor control of the limbs and torso; however, while the results tend to vary, there is a growing body of literature surrounding postural stability of the vocal tract (e.g., Barlow, Iacono, Paseman, Biswas, & D'Antonio, 1998). This is of particular interest because the inability to maintain adequate postural stability may negatively affect articulatory precision as well as vowel quality (Gerratt, 1983). In examining the degree of oral control, researchers typically employ assessments of force (ramp-and-hold technique; Barlow & Burton, 1990). Individuals with Parkinson's disease are thought to have an inability to select an adequate amount of force (or generate a large enough movement) in order to reach the target position during an activity (Jankovic & Tolosa, 1993). when an unimpaired individual experiences an episode of postutal instability, fast movements, with the appropriate amount of force, may be applied to return the body or structure to the target position (Shivitz, Koop, Fahimi, Heit, Bronte-Stewart, 2006). The inability to recruit an adequate amount of force for corrective movements can further contribute to postural instability. In building on prior knowledge of improvements in limb control in Parkinson's disease (e.g., Lozano et al., 1995), force measurements have been applied to gain a better understanding of the effects of surgical intervention on oral control. Gentil, Garcia-Ruiz, Pollak, and Benabid (1999) conducted an experiment with 10 participants examining the effect of electrical stimulation of the subthalamic nucleus on oral control. In the study, force measurements of the lips and tongue were assessed during stimulation and 1 hour following stimulation. Results indicated an increase in force of the articulators during stimulation. The hold phase of the stimulated patients was noted to be more accurate and steadier than that of the unstimulated patients who were unable to maintain contractions of the articulators. Similar findings have been reported by Barlow et al. (1998) following pallidotomy.
Another, noninvasive, treatment method that also appears to affect brain function in Parkinson's...
|
