Factors Influencing the Effects of Delayed Auditory Feedback on Dysarthric Speech Associated with Parkinson ’s Disease

Paul R Hoffman

doi:10.4172/2375-4427.1000106

Abstract

Purpose: The present study examined the effects of Delayed Auditory Feedback (DAF) as a rate control intervention for dysarthric speakers with Parkinson's disease. Adverse reactions to relatively long delay intervals are often observed during clinical use of DAF, and may result from improper matching of the delayed signal. To facilitate optimal use of DAF, clinicians may need to provide instruction, modeling, and feedback. Therefore, the primary purpose of this study was to evaluate the impact of clinician instruction on the effectiveness of DAF in treating speech deficits. A related purpose was to compare the effects of different delay intervals on speech behaviors. Method: Three males with Parkinson's disease and an associated dysarthria served as participants in this singlesubject study. The A phases consisted of a sentence reading task using DAF; the B phases incorporated clinician instruction. During each of the 16 experimental sessions, speakers read with four different delay intervals (0 ms, 50 ms, 100 ms, and 150 ms). During the B phases, the experimenter provided verbal feedback and modeling pertaining to how precisely the speaker matched the delayed signal. Dependent variables were speech rate, percent intelligible syllables, and percent disfluencies. Results: Results indicated that for all three speakers, DAF significantly reduced reading rate and produced significant improvements in either intelligibility (Speaker 3) or fluency (Speakers 1 and 2). A delay interval of 150 ms produced the greatest reductions in reading rates for all speakers, although any DAF setting used was sufficient to produce significant improvements in either intelligibility or fluency. Additionally, supplementing DAF with clinician instruction resulted in significantly enhanced gain achieved with DAF. Conclusions: These findings demonstrated the effectiveness of various intervals of DAF in improving speech deficits associated with Parkinson's disease; particularly when patients are provided with instruction, modeling and feedback by the clinician.

Highlights

Hypokinetic dysarthria is a motor speech disorder resulting from disturbances in muscular control secondary to neurological damage [1,2]
System (Casa Futura Technologies), a portable unit capable of producing delay intervals of up to 250 ms in duration.All speakers wore a head-mounted microphone/headphone assembly (Labtec, model C-324).This assembly was connected to the Delayed Auditory Feedback (DAF) unit, and an additional microphone was clipped onto the speaker's shirt and connected to a portable cassette tape recorder (Sony, model WMD6C).This procedure permitted audio recordings that were later used for reliability checks.All sessions were recorded onto TDK D60 audiocassette tapes
The four lines plotted on each graph represent the four DAF conditions utilized during each session (i.e., 0 ms, 50 ms, 100 ms, and 150 ms).Each graph is divided into four sections, which display data for the four phases of the experiment (i.e., A1, B1, A2, and B2).During each A phase, each participant read the sentences while using DAF without instruction and modeling from the experimenter.The experimenter provided instruction in conjunction with the use of DAF during the two B phases

Summary

Introduction

Hypokinetic dysarthria is a motor speech disorder resulting from disturbances in muscular control secondary to neurological damage [1,2]. This type of dysarthria was dubbed "hypokinetic" based on the view that its physiological basis involved a reduction in the range of movements needed for speech production. Perceptual features of hypokinetic dysarthria typically include imprecise consonant articulation, reduced variability of pitch and loudness, variable speech rate, short rushes of speech, and inappropriate or excessive silences [3,2]. Fluency deficits impacting rate and intelligibility often include sound or syllable repetitions, difficulty initiating phonation, and palilalia (i.e., involuntary repetition of words or phrases) [6]

Objectives

Methods

Results