Jason A. Whitfield

Articulatory-acoustic vowel space: application to clear speech in individuals with Parkinson's disease.

BACKGROUND/PURPOSE Individuals with Parkinson disease (PD) often exhibit decreased range of movement secondary to the disease process, which has been shown to affect articulatory movements. A number of investigations have failed to find statistically significant differences between control and disordered groups, and between speaking conditions, using traditional vowel space area measures. The purpose of the current investigation was to evaluate both between-group (PD versus control) and within-group (habitual versus clear) differences in articulatory function using a novel vowel space measure, the articulatory-acoustic vowel space (AAVS). METHODS The novel AAVS is calculated from continuously sampled formant trajectories of connected speech. In the current study, habitual and clear speech samples from twelve individuals with PD along with habitual control speech samples from ten neurologically healthy adults were collected and acoustically analyzed. In addition, a group of listeners completed perceptual rating of speech clarity for all samples. RESULTS Individuals with PD were perceived to exhibit decreased speech clarity compared to controls. Similarly, the novel AAVS measure was significantly lower in individuals with PD. In addition, the AAVS measure significantly tracked changes between the habitual and clear conditions that were confirmed by perceptual ratings. CONCLUSIONS In the current study, the novel AAVS measure is shown to be sensitive to disease-related group differences and within-person changes in articulatory function of individuals with PD. Additionally, these data confirm that individuals with PD can modulate the speech motor system to increase articulatory range of motion and speech clarity when given a simple prompt. LEARNING OUTCOMES The reader will be able to (i) describe articulatory behavior observed in the speech of individuals with Parkinson disease; (ii) describe traditional measures of vowel space area and how they relate to articulation; (iii) describe a novel measure of vowel space, the articulatory-acoustic vowel space and its relationship to articulation and the perception of speech clarity.

Speech Motor Sequence Learning: Acquisition and Retention in Parkinson Disease and Normal Aging

Purpose The aim of the current investigation was to examine speech motor sequence learning in neurologically healthy younger adults, neurologically healthy older adults, and individuals with Parkinson disease (PD) over a 2-day period. Method A sequential nonword repetition task was used to examine learning over 2 days. Participants practiced a sequence of 6 monosyllabic nonwords that was retested following nighttime sleep. The speed and accuracy of the nonword sequence were measured, and learning was inferred by examining performance within and between sessions. Results Though all groups exhibited comparable improvements of the nonword sequence performance during the initial session, between-session retention of the nonword sequence differed between groups. Younger adult controls exhibited offline gains, characterized by an increase in the speed and accuracy of nonword sequence performance across sessions, whereas older adults exhibited stable between-session performance. Individuals with PD exhibited offline losses, marked by an increase in sequence duration between sessions. Conclusions The current results demonstrate that both PD and normal aging affect retention of speech motor learning. Furthermore, these data suggest that basal ganglia dysfunction associated with PD may affect the later stages of speech motor learning. Findings from the current investigation are discussed in relation to studies examining consolidation of nonspeech motor learning.

Speech Motor Sequence Learning: Effect of Parkinson Disease and Normal Aging on Dual-Task Performance

Purpose Everyday communication is carried out concurrently with other tasks. Therefore, determining how dual tasks interfere with newly learned speech motor skills can offer insight into the cognitive mechanisms underlying speech motor learning in Parkinson disease (PD). The current investigation examines a recently learned speech motor sequence under dual-task conditions. Method A previously learned sequence of 6 monosyllabic nonwords was examined using a dual-task paradigm. Participants repeated the sequence while concurrently performing a visuomotor task, and performance on both tasks was measured in single- and dual-task conditions. Results The younger adult group exhibited little to no dual-task interference on the accuracy and duration of the sequence. The older adult group exhibited variability in dual-task costs, with the group as a whole exhibiting an intermediate, though significant, amount of dual-task interference. The PD group exhibited the largest degree of bidirectional dual-task interference among all the groups. Conclusions These data suggest that PD affects the later stages of speech motor learning, as the dual-task condition interfered with production of the recently learned sequence beyond the effect of normal aging. Because the basal ganglia is critical for the later stages of motor sequence learning, the observed deficits may result from the underlying neural dysfunction associated with PD.

Voicing contrast of stop consonant production in the speech of individuals with Parkinson disease ON and OFF dopaminergic medication

ABSTRACT The aims of this study were to: 1) compare voicing contrast in speakers with Parkinson disease (PD) and healthy controls by comparing the separation of voice onset time (VOT) distributions of voiced and voiceless stop consonants and 2) to determine whether the administration of dopaminergic medication affected VOT separation in speakers with PD. Data from a previous study by Fisher and Goberman (2010) were used to compare the VOT measures obtained from a group of speakers with PD with both ON and OFF medication, and a group of healthy controls. Supplementing the previous findings, the current analysis revealed that individuals with PD exhibited significantly less contrast between voiced and voiceless VOT than that observed in healthy speakers. Medication administration did not affect VOT contrast as no differences in VOT separation were observed between the ON and OFF medication states.

Fluency adaptation in speakers with Parkinson disease: a motor learning perspective

Abstract Purpose: Fluency adaptation is characterised by a reduction in stuttering-like behaviours over successive readings of the same speech material and is an effect that is typically observed in developmental stuttering. Prominent theories suggest that short-term motor learning associated with practice explain, in part, fluency adaptation. The current investigation examined the fluency adaptation effect in a group of speakers with Parkinson disease (PD) who exhibited stuttering-like disfluencies. Method: Individuals with PD (n = 21) and neurologically healthy controls (n = 19) read a passage five times. Per cent syllables stuttered was measured and calculated for each reading passage. Result: Participants in the PD group exhibited significantly more stuttering-like disfluencies than control speakers. Twelve individuals in the PD group exhibited at least three per cent syllable stuttered on at least one reading. Statistical trends revealed that the subgroup of individuals with PD who stuttered exhibited a significant reduction in stuttering moments over the five successive readings. Conclusion: A significant fluency adaptation effect was observed for the group of speakers with PD who exhibited stuttering-like disfluencies. Results of the current study are discussed within the framework of the motor learning hypothesis of fluency adaptation.

The effect of Parkinson disease on voice onset time: Temporal differences in voicing contrast

Parkinson disease (PD) affects the basal ganglia, which is involved with the selection, sequencing, and implementation of movement. Investigations suggest an extension of deficits to the speech motor and linguistic systems. Previous studies examining voice onset time (VOT) suggest that VOTs are neither systematically delayed nor systematically advanced in PD as compared to controls. The VOTs for voiced and voiceless stops are expected to differ for both individuals with PD and controls. However, inefficiencies in the sequencing and implementation of the voicing gesture may result in a smaller difference between VOT values of voiced and voiceless cognates. The current study examined VOT in individuals with PD and controls. Participants produced a corpus of stimuli to evaluate VOT using the carrier phrase “CVp again.” The four corner vowels and all stop consonants were used. Speech was recorded and VOT values were manually measured for every utterance. Overall VOTs were significantly shorter for voiceless s...