Academic journal article Journal of Medical Speech - Language Pathology

Tongue Function in Nondysarthric Speakers with Parkinson's Disease: An Electromagnetic Articulography Investigation

Academic journal article Journal of Medical Speech - Language Pathology

Tongue Function in Nondysarthric Speakers with Parkinson's Disease: An Electromagnetic Articulography Investigation

Article excerpt

Articulatory imprecision in Parkinson's disease (PD) has been attributed to reduced range of movement, rigidity, and abnormal speed of movement of the articulatory structures. Previous studios provided acoustic and kinematic evidence of lip muscle rigidity, reduced amplitude, and velocity of lip and jaw movement, mainly based on nonspeech measures. Very limited studies have documented the effects of PD on lingual kinematics during speech production. The present study aimed to investigate lingual kinematics during sentence production in a group of 7 nondysarthric speakers with PD using the electromagnetic articulograpb (AG-200 EMA). Tongue-tip and tongue-back movements were recorded by the EMA system during sentence production. Seven non-neurologically impaired participants matched for age and sex served as a control group. Results revealed no significant difference on the distance of tongue movement. However, the PD group did show significantly reduced maximum velocity, maximum acceleration, maximum deceleration, and significantly longer duration of tongue movement. Rates of sentence production were also slower for the PD group. The subclinical differences in tongue kinematics of the nondysarthric speakers with PD documented in this study support that limitations in the range of tongue movement leading to articulatory undershoot may be a major contributor to articulatory impairment in dysarthric speakers with PD.

INTRODUCTION

Hypokinetic dysarthria was first introduced by Darley, Aronson, and Brown (1969a, 1969b) based on their systematic analysis of speech characteristics in individuals with idiopathic Parkinson's disease (PD). Other than some prominent changes in prosody, precision of consonant articulation was reported to be significantly impaired in individuals with PD. Darley et al. (1969a, 1969b) hypothesized that limited range of movement, slowness of movement, muscle rigidity, and reduced force of movement contributed to the imprecision of consonant articulation in dysarthric speakers with PD. The orofacial muscle hypokinesia in individuals with PD was believed to be similar to limb bradykinesia marked by slow and limited range of movement (Darley, Aronson & Brown, 1975). Evidence from some acoustic and physiological investigations of speech supported this hypothesis (Ackermann & Ziegler, 1991; Forrest, Weismer & Turner, 1989; Hunker, Abbs & Barlow, 1982).

Hunker, Abbs, and Barlow (1982) conducted a quantitative analysis of labial muscle rigidity in Parkinsonian patients and proposed a causal relationship between labial rigidity and hypokinetic dysarthria. Ackermann and Ziegler (1991) analyzed the sentence utterances produced by 12 participants with PD acoustically. Although the participants with PD were reported to have compatible speech tempo to normal controls, their capacity for completing articulatory occlusion was significantly reduced. The authors described the reduction in movement amplitude of the articulators as articulatory "undershoot." Forrest, Weismer, and Turner (1989) conducted perceptual, acoustic, and kinematic analyses on the speech of Parkinsonian and normal geriatric adults and found that the Parkinsonian speakers--compared to normal geriatrics--had reduced lip movement amplitude and velocity during opening gestures but greater lip movement amplitude and velocity during closing gestures. Very limited jaw movement in the Parkinsonian speakers was also reported. Forrest et al. (1989), however, observed that many of their acoustic data results were not able to be related to kinematic events, which may be due to the lack of data on tongue movement, which was not accessible using the strain gauge system used in their study (Forrest et al., 1989).

Although there were some previous studies on tongue function in individuals with PD and documented reduced tongue force, impaired fine force control, and compromised endurance, these were largely based on nonspeech measures (Dworkin & Aronson, 1986; Solomon, Lorell, Robin, Rodnitzky & Luschei, 1995; Solomon, Robin & Luschei, 2000). …

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