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

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.

Gender Perception of Speech: Dependence on Fundamental Frequency, Implied Vocal Tract Length, and Source Spectral Tilt.

OBJECTIVE: To investigate how listeners use fundamental frequency, implied vocal tract length, and source spectral tilt to infer speaker gender. METHODS: Sound files each containing the vowels /i, æ, ɑ, u/ interspersed by brief silences were synthesized. Each of the 210 stimuli was a combination of 10 values for fundamental frequency and 7 values for implied vocal tract length (and the associated formant frequencies) ranging from male-typical to female-typical, and 3 values for source spectral tilt approximating the voice qualities of breathy, normal, and pressed. Twenty-three listeners judged each synthesized "speaker" as "female" or "male." Generalized linear mixed model analysis was used to determine the extent to which fundamental frequency, implied vocal track length, and spectral tilt influenced listener judgment. RESULTS: Increasing fundamental frequency and decreasing implied vocal tract length resulted in increased probability of female judgment. Two interactions were identified: An increase in fundamental frequency and also a decrease in source spectral tilt (more negative) resulted in a greater increase in the probability of female judgment when the vocal tract length was relatively short. CONCLUSIONS: The relationships among fundamental frequency, implied vocal tract length, source spectral tilt, and probability of female judgment changed across the range of normal values, suggesting that the relative contributions of fundamental frequency and implied vocal tract length to gender perception varied over the ranges studied. There was no threshold of fundamental frequency or implied vocal tract length that dramatically shifted the perception between male and female.

Cross-Cultural Adaptation, Validation, and Diagnostic Accuracy of the Voice Fatigue Handicap Questionnaire-Persian Version.

OBJECTIVE: The current study aimed to determine the psychometric characteristics of a translated version of the Voice Fatigue Handicap Questionnaire in Persian by examining the validity, reliability, and diagnostic accuracy using data collected from people with and without dysphonia. STUDY DESIGN: Cross-sectional study. METHOD: The original questionnaire was translated from Italian to Persian using the International Quality of Life Assessment criteria. The translated version was completed by 122 people with dysphonia and 49 people without dysphonia. The validity, reliability, and diagnostic accuracy of the Voice Fatigue Handicap Questionnaire Persian-version were evaluated. A panel of five voice-specializing Speech and Language Pathologists and 20 native Persian speakers (with dysphonia) in a pilot study confirmed the translated version for content and face validity, respectively. The internal consistency was evaluated by Cronbach's alpha and McDonald omega coefficients. The intraclass correlation coefficient was used to examine the test-retest reliability. For discriminant validity, the mean total and subscale scores of respondents with and without dysphonia were compared through independent t tests. Finally, sensitivity, specificity, and ideal cut-off value were determined using the receiver-operating characteristic curve. RESULTS: Cronbach's alpha coefficient was 0.965 for the total score (functional: α = 0.883, emotional: α = 0.944, physical: α = 0.917). Also, the McDonald omega coefficient was 0.966 for the total score (functional: ω = 0.889, emotional: ω = 0.933, physical: ω = 0.920). The intraclass correlation coefficient for measuring the test-retest reliability was 0.971 for the total score (functional: ICC=0.937, emotional: ICC=0.954, physical ICC=0.976). The results of the independent samples t tests indicated that the dysphonia group obtained significantly higher mean scores (total and subscale scores) than the group without dysphonia. The cutoff value of 13.5 was determined based on the optimal balance of sensitivity (0.992) and specificity (0.918). CONCLUSION: The Voice Fatigue Handicap Questionnaire-Persian version is a valid and reliable questionnaire to identify individuals at high risk of vocal fatigue and subsequent dysphonia.

Systemic Racism in Communication Sciences and Disorders Academic Programs: A Commentary on Trends in Racial Representation.

PURPOSE: As a discipline, communication sciences and disorders (CSD) has struggled to address equity and inclusion for students, professionals, and scholars from historically excluded racial groups. Recent publications in this periodical that have begun to confront systemic racism in the discipline have been met with some expected resistance. In this commentary, I attempt to support and expand an argument made by Ellis and Kendall (2021), namely, that systemic racism has been and continues to be a normal and persistent feature of our academic programs. A comparison to U.S. Census data suggests that Asian, Black, Indigenous, Native, Latino/a/e, and multiracial CSD professionals are represented to a drastically lower rate compared with their representation in the population at large. Furthermore, publicly available data summaries indicate that there is a reduction in the level of racial diversity that is associated with an increase in White representation across the entire progression of the professional training and certification process, with the greatest level of diversity at the undergraduate level followed by the graduate and professional levels. CONCLUSIONS: A general knowledge of social and legal history in the United States would suggest that the relative reduction in representation across the academic and professional levels of the CSD disciplines results from policy and practice patterns that serve to preserve a White-dominant culture in our profession and exclude People of Color. Continued efforts broadly based in critical race studies may prove as a useful tool to identify, confront, and transform current policy and practice patterns in our national organization, academic programs, and accrediting bodies that have produced and sustained levels of inequality and White dominance in our programs and disciplines.

Effect of clear speech on acoustic measures of dysprosody in Parkinson disease for different reading tasks.

PURPOSE: The purpose of the study was to determine the effect of clear speech instruction on acoustic measures of dysprosody between reading passages of differing linguistic content for speakers with and without Parkinson Disease (PD). METHOD: Ten speakers with PD and 10 controls served as participants and read five simple and three standard reading stimuli twice. First, speakers read habitually and then following clear speech instruction. Acoustic measures of fundamental frequency variation (semitone standard deviation, STSD), articulation rate, and between-complex pause durations were calculated. RESULT: Results indicated speakers with PD exhibited less fundamental frequency variation than controls across reading stimuli and instructions. All speakers exhibited lower STSD and longer between-complex pause durations for the standard compared to simple reading stimuli. For clear speech, all speakers reduced articulation rate and increased between-complex pause durations in both simple and standard reading stimuli. However, speakers with PD exhibited a significantly less robust reduction in articulation rate for clear speech than control speakers for all reading stimuli. CONCLUSION: Linguistic content of reading stimuli contributes to differences in fundamental frequency variation and pause duration for all speakers. All speakers reduced articulation rate for clear speech compared to habitual instruction, but speakers with PD did so to a lesser extent than controls. Linguistic content of reading stimuli to examine dysprosody in PD should be considered for clinical application.

Quantifying Spatial and Temporal Variability of Clear and Loud Speech Produced While Performing a Concurrent Visuomotor Task.

PURPOSE: The purpose of this research note was to quantify the impact of concurrent performance of an attention-demanding secondary task on utterance-to-utterance movement variability associated with higher effort speaking styles, namely, clear and loud speech. METHOD: Lip and jaw kinematics collected as part of a prior study were analyzed. Participants repeated "Buy Bobby a puppy" using habitual, loud, and clear speech styles in isolation and while performing a secondary tracking task. The lip aperture (LA) signal was segmented based on opening and closing gestures associated with the utterance. The standard deviation of each segment duration was calculated to quantify temporal variability. To quantify spatial variability, each segment was first time normalized. The mean standard deviation of the overlapping time-normalized LA amplitudes was computed for each segment from the repetitions produced in each speech style and condition (speaking in isolation vs. speaking while tracking). A relative measure of spatial variation was also computed to account for the potential impact of articulatory scaling. RESULTS: Clear speech was associated with greater temporal and spatial variability than the habitual and loud styles. In the habitual style, talkers also exhibited a slight reduction in absolute spatial variability when speaking while tracking compared to speaking in isolation. The reduction in absolute spatial variability was likely associated with the concomitant reduction in LA range of motion, as there was no change in the relative spatial variability between conditions. CONCLUSION: The current investigation expands prior work by quantifying spatial and temporal characteristics of different speaking styles performed in isolation and while concurrently performing an attention-demanding visuomotor task.

Order Affects Clear and Loud Speech Response.

PURPOSE: The purpose of this investigation was to examine the impact of instruction order on the speech production response when adopting higher effort speaking styles, specifically loud and clear speech. METHOD: Speech intensity, lip aperture range, and speech rate data were collected from 24 talkers who repeated the utterance "Buy Bobby a puppy" using habitual, clear, and loud speech. Participants were assigned in quasi-random fashion to one of two groups: a Clear-Loud Group (11 participants; order: habitual-clear-loud) or a Loud-Clear Group (13 participants; order: habitual-loud-clear). RESULTS: Talkers in the Clear-Loud Group exhibited higher speech intensity during the loud style compared with those who performed the Loud-Clear Group. Furthermore, talkers in the Clear-Loud Group retained the increases lip aperture range and reductions in speech rate associated with the clear style when producing the loud style. Conversely, talkers in the Loud-Clear Group exhibited significant increases in lip aperture range between the habitual and loud styles and between the loud and clear styles. Additionally, the Loud-Clear Group exhibited a reduction in speech rate only during the clear style, as no differences in speech rate were observed between the habitual and loud styles. CONCLUSIONS: These findings may suggest that producing a higher effort style leads to carry-over effects in subsequent styles. Future research should investigate factors that moderate the degree of order effects for both research and clinical purposes. For instance, if generalizable, the compounding carry-over effects may prove advantageous for certain clinical populations.

Reliability of a Linguistic Segmentation Procedure Specified by Systemic Functional Linguistics to Examine Extemporaneous Speech.

PURPOSE: Extemporaneous speech tasks provide an ecologically valid sample to examine speech acoustics, but differing methodologies exist in the literature for segmentation. Therefore, the purpose of this study was to examine the utility and reliability of a segmentation approach for extemporaneous speech specified by systemic functional linguistics (SFL) and its potential research and clinical applications. METHOD: Ten speakers without communication disorders served as participants in this study, and they responded to self-selected extemporaneous speaking prompts. Two expert analysts and one clinician analyst utilized a segmentation procedure specified by SFL to segment the extemporaneous speech samples into clauses and clause complexes. Intra- and interrater reliability were calculated for each analyst and pair of analysts. Acoustic measures of duration, speech rate, and intercomplex pause durations were calculated for each clause complex. RESULTS: Analyses for both intra- and interrater reliability revealed high percent agreement that was significantly greater than chance for expert and clinician analysts and between each pair of analysts (p < .001). Acoustic analyses revealed expected variation in number and duration of spoken syllables of clause complexes between and within speakers. CONCLUSIONS: The segmentation approach for extemporaneous speech specified by SFL is a reliable method for trained analysts that is informed by lexico-grammar and allows for acoustic measurement of speech production. It is also a reliable method for clinician analysts for speakers without communication disorders, and future work will investigate its utility for speakers with motor speech disorders. SUPPLEMENTAL MATERIAL: https://doi.org/10.23641/asha.22357138.

Practice Mediates Bidirectional Dual-Task Interference When Performing a Novel Sequential Nonword Repetition Task.

Introduction The current study examined the extent to which practice amount mediates dual-task interference patterns associated with concurrent performance of a novel speech task and attention-demanding visuomotor task. Method A Sequential Nonword Repetition Task was used to examine the effect of practice on interference associated with concurrent performance of a Visuomotor Pursuit Task. Twenty-five young adult participants were assigned to either an Extended Practice Group or a Limited Practice Group and performed a novel Sequential Nonword Repetition Task in isolation and while performing a concurrent visuomotor pursuit rotor task. Results Participants in the Limited Practice Group who were afforded a limited amount of practice exhibited dual-task interference (i.e., dual-task performance reductions) for both the speech and visuomotor tasks (i.e., bidirectional dual-task interference). Conversely, participants in the Extended Practice Group who were afforded extended practice exhibited little-to-no observable dual-task interference on the nonword repetition task. Conclusion Data from the current investigation suggest that the amount of initial practice mediates the degree of dual-task interference observed when a novel speech production task is performed with an attention-demanding Visuomotor Pursuit Task. Supplemental Material https://doi.org/10.23641/asha.14608071.

Tracking the Costs of Clear and Loud Speech: Interactions Between Speech Motor Control and Concurrent Visuomotor Tracking.

Purpose Prior work has demonstrated that competing tasks impact habitual speech production. The purpose of this investigation was to quantify the extent to which clear and loud speech are affected by concurrent performance of an attention-demanding task. Method Speech kinematics and acoustics were collected while participants spoke using habitual, loud, and clear speech styles. The styles were performed in isolation and while performing a secondary tracking task. Results Compared to the habitual style, speakers exhibited expected increases in lip aperture range of motion and speech intensity for the clear and loud styles. During concurrent visuomotor tracking, there was a decrease in lip aperture range of motion and speech intensity for the habitual style. Tracking performance during habitual speech did not differ from single-task tracking. For loud and clear speech, speakers retained the gains in speech intensity and range of motion, respectively, while concurrently tracking. A reduction in tracking performance was observed during concurrent loud and clear speech, compared to tracking alone. Conclusions These data suggest that loud and clear speech may help to mitigate motor interference associated with concurrent performance of an attention-demanding task. Additionally, reductions in tracking accuracy observed during concurrent loud and clear speech may suggest that these higher effort speaking styles require greater attentional resources than habitual speech.

Effect of Clear Speech on the Duration of Silent Intervals at Syntactic and Phonemic Boundaries in the Speech of Individuals With Parkinson Disease.

Purpose The purpose of the current investigation was to determine the extent to which individuals with and without Parkinson disease (PD) modified silent interval durations when using a clear speaking style. Method Ten individuals with idiopathic PD and 10 older adult control speakers produced a reading passage using both habitual and clear speaking styles. Silent intervals lasting 15 ms and longer were identified and extracted. Each silent interval was categorized according to the surrounding syntactic context of the reading passage. In addition, voiceless stop gaps that occurred within words, phrases, or clauses were categorized by the preceding phonemic context. Results Statistical analyses revealed that all participants increased silent interval duration with a clear speaking style at inter-sentence and intra-sentence syntactic boundaries. Compared to controls, individuals with PD exhibited significantly less increase in silent interval durations at these syntactic boundaries. Control speakers also increased silent stop gap durations in the clear speaking style regardless of preceding phonemic context. Individuals with PD, however, only increased stop gap duration when the silent interval was preceded by a sonorant. Conclusion These findings suggest that speakers with PD exhibit less clarity-related increase in silent interval duration than control speakers. In addition, speakers with PD exhibited significant increases in silent interval duration that coincided with syntactic boundaries of the reading passage but little to no clarity-related modulation of stop gap intervals. Therefore, these data suggest that speakers with PD exhibited changes in silent interval durations that were more so associated with modulation of speech prosody than articulation when using a clearer speaking style.

Examination of Clear Speech in Parkinson Disease Using Measures of Working Vowel Space.

Purpose The purpose of the current study was to characterize clear speech production for speakers with and without Parkinson disease (PD) using several measures of working vowel space computed from frequently sampled formant trajectories. Method The 1st 2 formant frequencies were tracked for a reading passage that was produced using habitual and clear speaking styles by 15 speakers with PD and 15 healthy control speakers. Vowel space metrics were calculated from the distribution of frequently sampled formant frequency tracks, including vowel space hull area, articulatory-acoustic vowel space, and multiple vowel space density (VSD) measures based on different percentile contours of the formant density distribution. Results Both speaker groups exhibited significant increases in the articulatory-acoustic vowel space and VSD10, the area of the outermost (10th percentile) contour of the formant density distribution, from habitual to clear styles. These clarity-related vowel space increases were significantly smaller for speakers with PD than controls. Both groups also exhibited a significant increase in vowel space hull area; however, this metric was not sensitive to differences in the clear speech response between groups. Relative to healthy controls, speakers with PD exhibited a significantly smaller VSD90, the area of the most central (90th percentile), densely populated region of the formant space. Conclusions Using vowel space metrics calculated from formant traces of the reading passage, the current work suggests that speakers with PD do indeed reach the more peripheral regions of the vowel space during connected speech but spend a larger percentage of the time in more central regions of formant space than healthy speakers. Additionally, working vowel space metrics based on the distribution of formant data suggested that speakers with PD exhibited less of a clarity-related increase in formant space than controls, a trend that was not observed for perimeter-based measures of vowel space area.

Characterizing the distribution of silent intervals in the connected speech of individuals with Parkinson disease.

The purpose of the current investigation was to examine a statistical approach to differentiating shorter silent intervals (e.g., stop gaps) from longer silent intervals (e.g., pause) at varying syntactic locations within a reading passage to better characterize articulatory and prosodic aspects of speech timing in Parkinson disease (PD). Silent intervals 15 ms and longer were extracted from reading sample. Logarithmic transformation of the silent interval durations yielded a bimodal distribution. Gaussian Mixture Model analysis was used to statistically differentiate the first mode (Mode 1) that corresponded to short silent intervals from the second mode (Mode 2) that corresponded to longer silent intervals. The syntactic context surrounding each silent interval was also categorized. Results revealed that the large majority of silent intervals that occurred within a clause, phrase, or word were assigned to Mode 1, while the majority of silent intervals that coincided with sentence-ending punctuation were assigned to Mode 2. Results revealed that Mode 1 intervals were slightly, but significantly longer for speakers with PD (Mean = 52.48 ms, SE = 3.23) compared to controls (Mean = 44.67 ms, SE = 2.00). Examination of the surrounding syntactic context revealed that this difference occurred at between-word boundaries contained within a phrase or clause. No between group differences were observed for the other inter- and intra-sentence syntactic boundaries or Mode 2 intervals. This study outlines a data-based approach to differentiating short between- and within-word intervals from longer silent intervals or pauses that reflect the prosodic and syntactic structure of a reading passage. Using this approach, the current data suggest that speakers with PD exhibit longer short silent intervals than controls, potentially reflecting a slight delay in the fluent segment-to-segment transition between words.

Signal Interpretation Considerations When Estimating Subglottal Pressure From Oral Air Pressure.

Purpose Oral air pressure measurements during lip occlusion for /pVpV/ syllable strings are used to estimate subglottal pressure during the vowel. Accuracy of this method relies on smoothly produced syllable repetitions. The purpose of this study was to investigate the oral air pressure waveform during the /p/ lip occlusions and propose physiological explanations for nonflat shapes. Method Ten adult participants were trained to produce the "standard condition" and were instructed to produce nonstandard tasks. Results from 8 participants are included. The standard condition required participants to produce /pːiːpːiː.../ syllables smoothly at approximately 1.5 syllables/s. The nonstandard tasks included an air leak between the lips, faster syllable repetition rates, an initial voiced consonant, and 2-syllable word productions. Results Eleven oral air pressure waveform shapes were identified during the lip occlusions, and plausible physiological explanations for each shape are provided based on the tasks in which they occurred. Training the use of the standard condition, the initial voice consonant condition, and the 2-syllable word production increased the likelihood of rectangular oral air pressure waveform shapes. Increasing the rate beyond 1.5 syllables/s improved the probability of producing rectangular oral air pressure signal shapes in some participants. Conclusions Visual and verbal feedback improved the likelihood of producing rectangular oral air pressure signal shapes. The physiological explanations of variations in the oral air pressure waveform shape may provide direction to the clinician or researcher when providing feedback to increase the accuracy of estimating subglottal pressure from oral air pressure.

Effects of Concurrent Manual Task Performance on Connected Speech Acoustics in Individuals With Parkinson Disease.

Purpose Prior investigations suggest that simultaneous performance of more than 1 motor-oriented task may exacerbate speech motor deficits in individuals with Parkinson disease (PD). The purpose of the current investigation was to examine the extent to which performing a low-demand manual task affected the connected speech in individuals with and without PD. Method Individuals with PD and neurologically healthy controls performed speech tasks (reading and extemporaneous speech tasks) and an oscillatory manual task (a counterclockwise circle-drawing task) in isolation (single-task condition) and concurrently (dual-task condition). Results Relative to speech task performance, no changes in speech acoustics were observed for either group when the low-demand motor task was performed with the concurrent reading tasks. Speakers with PD exhibited a significant decrease in pause duration between the single-task (speech only) and dual-task conditions for the extemporaneous speech task, whereas control participants did not exhibit changes in any speech production variable between the single- and dual-task conditions. Conclusions Overall, there were little to no changes in speech production when a low-demand oscillatory motor task was performed with concurrent reading. For the extemporaneous task, however, individuals with PD exhibited significant changes when the speech and manual tasks were performed concurrently, a pattern that was not observed for control speakers. Supplemental Material https://doi.org/10.23641/asha.8637008.

Examining Acoustic and Kinematic Measures of Articulatory Working Space: Effects of Speech Intensity.

Purpose: The purpose of this study was to examine the effect of speech intensity on acoustic and kinematic vowel space measures and conduct a preliminary examination of the relationship between kinematic and acoustic vowel space metrics calculated from continuously sampled lingual marker and formant traces. Method: Young adult speakers produced 3 repetitions of 2 different sentences at 3 different loudness levels. Lingual kinematic and acoustic signals were collected and analyzed. Acoustic and kinematic variants of several vowel space metrics were calculated from the formant frequencies and the position of 2 lingual markers. Traditional metrics included triangular vowel space area and the vowel articulation index. Acoustic and kinematic variants of sentence-level metrics based on the articulatory-acoustic vowel space and the vowel space hull area were also calculated. Results: Both acoustic and kinematic variants of the sentence-level metrics significantly increased with an increase in loudness, whereas no statistically significant differences in traditional vowel-point metrics were observed for either the kinematic or acoustic variants across the 3 loudness conditions. In addition, moderate-to-strong relationships between the acoustic and kinematic variants of the sentence-level vowel space metrics were observed for the majority of participants. Conclusions: These data suggest that both kinematic and acoustic vowel space metrics that reflect the dynamic contributions of both consonant and vowel segments are sensitive to within-speaker changes in articulation associated with manipulations of speech intensity.

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

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.

Articulatory-acoustic vowel space: Associations between acoustic and perceptual measures of clear speech.

PURPOSE: The current investigation examined the relationship between perceptual ratings of speech clarity and acoustic measures of speech production. Included among the acoustic measures was the Articulatory-Acoustic Vowel Space (AAVS), which provides a measure of working formant space derived from continuously sampled formant trajectories in connected speech. METHOD: Acoustic measures of articulation and listener ratings of speech clarity were obtained from habitual and clear speech samples produced by 10 neurologically healthy adults. Perceptual ratings of speech clarity were obtained from visual-analogue scale ratings and acoustic measures included the AAVS measure, articulation rate and percentage pause. RESULT: Clear speech was characterised by a higher perceptual clarity rating, slower articulation rate, greater percentage pause and larger AAVS compared to habitual speech. Additionally, correlation analysis revealed a significant relationship between the perceptual clear speech effect and the relative clarity-related change in the AAVS and articulation rate measures. CONCLUSION: The current findings suggest that, along with speech rate measures, the recently introduced AAVS is sensitive to changes in speech clarity.

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.

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.