Sustained Vowel Phonation Research Articles

Neural representation of pitch-shifted voice feedback at N100 and P200 components: An event-related potentials (ERP) study

Numerous studies have shown that perturbations in voice pitch feedback lead to compensatory responses in voice fundamental frequency (F0), but few have reported on neural responses to the acoustical stimulation during the pitch-shifted voice feedback. In this study, randomized-onset, upward pitch-shift stimuli (60 ms duration) were presented to ten subjects during sustained vowel phonation while the event-related potentials (ERPs) were recorded through Cz-linked earlobe surface electrodes. ERPs were also recorded as subjects passively listened to the same feedback signal that was recorded during vocalization. The experimental task was repeated for 100, 200, and 500 cents conditions, respectively, and the results were compared in vocalization and listening conditions. Across three stimulus magnitudes, the N100 responses during vocalization were suppressed in comparison with those recorded in the passive-listening condition. On the other hand, the P200 responses in the passive-listening task were graded in amplitude according to the magnitude of the stimulus, with the smallest responses for 100 cents and largest for 500 cents stimuli. However, during vocalization, the P200 responses were found to be graded in the opposite way, where the largest responses were associated with 100 cents and the smallest with 500 cents stimuli.

The effect of levodopa on respiration and word intelligibility in people with advanced Parkinson's disease

Objectives Hypokinetic dysarthria is commonly encountered in Parkinson's disease (PD). Although the etiology of this dysarthria is multifactorial, disorders of respiration may strongly contribute to it. The aim of this study was to evaluate the effects of levodopa on measures of respiration and intelligibility. Patients and methods Vital capacity (VC), sustained vowel phonation (SVP) and phonation quotient (PQ) were determined with and without medication in 25 patients suffering from idiopathic PD. Intelligibility was evaluated by three independent speech pathologists using the word subtest protocol of the Yorkston and Beukelman “Assessment of intelligibility of dysarthric speech” (AIDS). Results VC was abnormal in 18/25 patients in the off-condition and 15/25 in the on-condition. SVP was normal in 22/25 patients in the off-state and in all patients in the on-state. PQ was normal in all patients in the off- and on-condition. All three respiratory parameters, as well as intelligibility, improved significantly following administration of levodopa. There were significant differences between men and women for VC and PQ, with men having the highest values for both parameters in both conditions. In none of the two conditions a correlation between respiratory parameters and intelligibility could be demonstrated. Conclusion This study suggests that thoracic mobility is decreased in PD, and that pharmacological treatment results in improvement, but not in normalization. Moreover, it remains unclear to what extent dyskinesias negatively influence respiratory control. Our results also demonstrate improvement of intelligibility after pharmacological treatment of PD. However, this improvement is not solely the consequence of respiratory changes. Further research on the effects of different characteristics on intelligibility is necessary.

Evaluating the effect of subthalamic deep brain stimulation on vocal function in Parkinson’s disease

The study reports the effect of subthalamic deep brain stimulation (STN DBS) on vocal function in Parkinson’s disease (PD). Specifically, the effect was evaluated in relation to the vibratory characteristics of the vocal folds during sustained vowel phonation using two different methods: one measures jitter and shimmer, while the other measures the correlation dimension D2, a nonlinear dynamic analysis. Twenty right-handed individuals with advanced PD and dysarthria underwent unilateral STN DBS. Ten were operated on the right hemisphere and ten on the left hemisphere. The side receiving STN DBS had more affected motor function. Speech was evaluated before surgery and three-to-six months after surgery with stimulator-off and with stimulator-on; all were off anti-Parkinsonian medication for 12 h before evaluation. Evaluators and subjects were blinded to the subjects stimulator status at the postsurgery evaluations. Nonspeech motor performance was assessed with UPDRS-III. Each subject produced six maximally sustained ‘‘ah’’ phonations (MSVPs) at his/her habitual loudness level. Two-second samples extracted from the MSVPs were used for both analyses. In addition, the maximum vocal intensity, duration, mean F0, and cycle-to-cycle F0 variation were also obtained. The results were discussed with regard to Chaos theory and the phonation characteristics in PD.

Role of voice F0 production accuracy and pitch perception ability in modifying compensatory voice F0 responses during sustained vowel productions

The purpose of the present study is to assess whether subject characteristics in terms of voice F0 production accuracy and pitch perception ability are related to the ability to compensate in real‐time for altered auditory feedback. To assess the relationship of vocal production, pitch‐perception, and voice F0 error‐correction, a series of three tasks were completed by typical college‐age participants: (1) A pitch‐matching task where participants vocally matched the pitch of audible complex tones, (2) two‐tone forced choice pitch‐discrimination tasks where participants decided if complex tone pairs (200 ms duration for each tone) sounded the same or different, and (3) pitch‐shifting tasks where participants produced sustained vowel phonations, while listening to experimentally altered auditory feedback (brief 200 ms pitch perturbations of +/−20, 60, or 100 cents were introduced into the feedback). Dependent measures of pitch‐matching accuracy, pitch‐discrimination sensitivity, and variations in the latency, stability, and magnitude of compensatory pitch‐shift reflexes were assessed in all participants. Pilot data (N=3) indicate that production accuracy and discrimination sensitivity does not play a role in compensatory control of the voice. Poor pitch‐matchers and/or discriminators actually respond to very small magnitude perturbations (20 cents) in a manner similar to accurate pitch‐matchers and/or perceivers.

PR_158: Voice and Choral Singing Treatment for Parkinson’s Disease Patients

Objective: To propose a new voice rehabilitation program for parkinsonian patients based on voice treatment and choral singing (VCST). Design: Pilot test-retest noncontrolled study. Setting: The voice and choral activity, directed by a speech therapist expert in Parkinson’s disease (PD) and choral singing, took place in a quiet room. Participants: 20 consecutive PD patients voluntarily participated in our VCST. All patients had a definite diagnosis of PD according to the clinical criteria of the United Kingdom Parkinson’s Disease Society Brain Bank. Interventions: From October 2003 to February 2004, patients underwent 20 hours of speech therapy, 2 sessions of 1 hour every week, and 26 hours of choral singing, 1 session of 2 hours every week. Main Outcome Measures: Forced vital capacity, forced expiratory volume in 1 second, functional residual capacity (FRC), maximum inspiratory pressure (MIP), maximum expiratory pressure (MEP); mean fundamental frequency, jitter percentage, fundamental frequency variation, shimmer percentage, peak amplitude variation, fundamental frequency tremor intensity index, amplitude tremor intensity index, maximum duration of sustained vowel phonation (MDPh); and prosodia reading a passage measured with a visual analog scale, presence of fatigue reading a passage, and prosodia and fatigue during conversational monologue. Results: Using paired t tests, we found a significant improvement of the following variables: percentage FRC (P=.033), MIP (P=.019), MEP (P=.006), MDPh (P=.000), and prosodia reading a passage (P=.046); using Wilcoxon signed-rank tests, we found a significant improvement of fatigue reading a passage (P=.05). No significant difference was found in the other variables taken into consideration. Conclusions: Our VCST for PD patients can improve specific abnormalities with an amusing, agreeable, collective approach. Our results are interesting, but, to find evidence of efficacy, we need to conduct a randomized clinical trial to compare VCST with another voice and speech therapy for PD (ie, the Lee Silverman voice treatment).

Communication Problems in Multiple Sclerosis: 9-Year Follow-Up

The speech of 18 individuals with a long history of multiple sclerosis (MS), assessed 9–10 years earlier, was reinvestigated. The individuals were also interviewed about their experiences of living with MS and how they have handled communication problems and symptoms in general. Findings were related to the degree of neurological deficit. The results showed that neurological deficits increased and certain speech parameters (sustained vowel phonation and speech rate) decreased significantly during this period. Speech intelligibility was not significantly changed (>90% at follow-up). Consequently, speech problems were generally mild. Nevertheless, analysis of the interviews showed that participation in communication and interpersonal relationships was affected by other disease-related (mobility, vision, cognition, and fatigue) and age-related problems. Strategies to reduce the effect of communication and disease-related problems were found to be active rather than adjustment or avoidance, both in specific situations and as an approach to life. In conclusion, the importance of a broader perspective on communication difficulties and a more individual approach to intervention should be emphasized, taking the patient's perceived barriers and self-generated strategies into account.

Phonatory Impairment in Parkinson's Disease: Evidence from Nonlinear Dynamic Analysis and Perturbation Analysis

Many persons with Parkinson's disease (PD) will eventually experience vocal impairment as their condition advances. Using standard perturbation analyses (parameters like jitter and shimmer) to measure fluctuations in phonatory signal may inhibit researchers from recognizing severely disordered patterns that seem to be present in the voices of some PD patients. Nonlinear dynamic analysis can quantify these aperiodic patterns, which indicate severe pathology that is usually characterized perceptually by hoarseness. Here, sustained vowel phonations of a heterogeneous group of PD subjects (20 women and 21 men) were compared with those of a control group (22 women and 18 men) based on results of nonlinear dynamic analyses (D(2)) and perturbation analyses. Results showed PD subjects as a whole to have significantly higher D(2) values than control subjects (P = 0.016), which indicates increased signal complexity in PD vocal pathology. Differences in the comparison of these two groups were significant in jitter (P = 0.014) but nonsignificant in shimmer (P = 0.695). Furthermore, the performance on these three measures was affected by subject sex. Nonlinear dynamic analysis showed significantly higher D(2) in the female PD group than in the female control group (P = 0.001), but jitter and shimmer did not show such a difference. The male PD group had statistically higher jitter than the male control group (P = 0.036), but these groups did not differ in D(2) or shimmer. Overall, nonlinear dynamic analysis may be a valuable method for the diagnosis of Parkinsonian laryngeal pathology.

Voice F0 responses elicited by perturbations in pitch of auditory feedback during English speech and sustained vowels

Twenty-one native speakers of American English were asked to repeatedly inflect the pitch of either the first or second syllable of an English speech phrase or produce non-word sustained vowels while listening to amplified auditory feedback. Brief upward and downward perturbations in pitch of auditory feedback were introduced in real time shortly after vocal onset. Resultant changes in voice F0 due to perturbations in pitch were compared across vocal conditions and perturbation direction. Data indicated that auditory feedback was used in real-time to stabilize voice F0 during both normal English speech and sustained vowels. Incomplete compensatory corrections in voice F0 due to the perturbations in pitch of auditory feedback were prevalent during both dynamic speech (gain: ∼12.7%) and static sustained vowel phonations (gain: ∼19.3%), and appear to be regulated by similar corrective mechanisms. However during dynamic speech, voice F0 was modulated across syllable boundaries in a task-dependent manner according to syllable pitch inflection. Thus, voice F0 responses appear to help maintain the underlying suprasegmental meaning of a speech phrase by delaying the onset of the voice F0 response to coincide with the pitch-inflected syllable. [Work supported by NIH Grant No. F31 DC005874.]

Voice responses to changes in pitch of voice or tone auditory feedback

The present study was undertaken to examine if a subject's voice F0 responded not only to perturbations in pitch of voice feedback but also to changes in pitch of a side tone presented congruent with voice feedback. Small magnitude brief duration perturbations in pitch of voice or tone auditory feedback were randomly introduced during sustained vowel phonations. Results demonstrated a higher rate and larger magnitude of voice F0 responses to changes in pitch of the voice compared with a triangular-shaped tone (experiment 1) or a pure tone (experiment 2). However, response latencies did not differ across voice or tone conditions. Data suggest that subjects responded to the change in F0 rather than harmonic frequencies of auditory feedback because voice F0 response prevalence, magnitude, or latency did not statistically differ across triangular-shaped tone or pure-tone feedback. Results indicate the audio-vocal system is sensitive to the change in pitch of a variety of sounds, which may represent a flexible system capable of adapting to changes in the subject's voice. However, lower prevalence and smaller responses to tone pitch-shifted signals suggest that the audio-vocal system may resist changes to the pitch of other environmental sounds when voice feedback is present.

Fragments of a Greek Trilogy: impact on phonation

Summary This study documents the vocal characteristics of an actor before and after a series of eight performances involving extended voice use. The hypothesis was that this type of extended voice use would result in symptoms of vocal abuse and that damage to the actor's voice would be evident in measures made after the performance series. Three pre-performance and three post-performance speech samples were gathered and analyzed using the CSL and Visipitch II. Measurements taken included maximum phonational range; maximum sustained phonation; fundamental frequency during reading; maximum intensity levels; sound pressure levels for soft, moderate, and loud productions of sustained /a/; and perturbation including jitter, shimmer, harmonics-to-noise ratio, and an s/z ratio. Pre- and post-performance samples of the “Rainbow passage” and sustained vowel phonation were rated by a group of blinded listeners that included professional voice trainers and speech pathologists. In addition, sample lines from the performance were played for the listeners to judge whether this technique would result in symptoms of vocal abuse. Eleven out of 12 professional voice trainers rated that this technique would result in symptoms of vocal abuse. The data revealed post-performance improvement in phonational range, maximum intensity levels, perturbation measures, and s/z ratio. Measures of maximum sustained phonation, fundamental frequency, and sound pressure levels remained stable. Videoendoscopy revealed normal function of the larynx and vocal folds.

The effect of unilateral electrostimulation of the subthalamic nucleus on respiratory/phonatory subsystems of speech production in Parkinson's disease—a preliminary report

This paper reports findings on the respiratory/phonatory subsystems from an on‐going study investigating the effect of unilateral electrostimulation of the subthalamic nucleus (STN) on different speech subsystems in people with Parkinson's disease (PD). Speech recordings were made in the medication‐off state at baseline, three months post surgery with stimulation‐on, and with stimulation‐off, in six right‐handed PD patients. Subjects completed several speech tasks. Acoustic analyses of the maximally sustained vowel phonation were reported. The results were compared to the scores of the motor section of the Unified Parkinson's Disease Rating Scale (UPDRS‐III) obtained under the same conditions. Results showed that stimulation‐on improved UPDRS‐III scores in all six subjects. While mild improvement was observed for all subjects in the Stimulation‐on condition, three subjects received left‐STN stimulation showed a significant decline in vocal intensity and vowel duration from their baseline indicating the speech function was very susceptible to micro lesions due to the surgical procedure itself when the surgical site was in the dominant hemisphere.

Cepstral peak prominence: a more reliable measure of dysphonia.

Quantification of perceptual voice characteristics allows the assessment of voice changes. Acoustic measures of jitter, shimmer, and noise-to-harmonic ratio (NHR) are often unreliable. Measures of cepstral peak prominence (CPP) may be more reliable predictors of dysphonia. Trained listeners analyzed voice samples from 281 patients. The NHR, amplitude perturbation quotient, smoothed pitch perturbation quotient, percent jitter, and CPP were obtained from sustained vowel phonation, and the CPP was obtained from running speech. For the first time, normal and abnormal values of CPP were defined, and they were compared with other acoustic measures used to predict dysphonia. The CPP for running speech is a good predictor and a more reliable measure of dysphonia than are acoustic measures of jitter, shimmer, and NHR.

Swallowing and voice effects of Lee Silverman Voice Treatment (LSVT®): a pilot study

Objective: To define the effects of Lee Silverman Voice Treatment (LSVT® on swallowing and voice in eight patients with idiopathic Parkinson's disease. Methods: Each patient received a modified barium swallow...

Intensive voice treatment (LSVT®) for patients with Parkinson's disease: a 2 year follow up

OBJECTIVESTo assess long term (24 months) effects of the Lee Silverman voice treatment (LSVT®), a method designed to improve vocal function in patients with Parkinson's disease.METHODSThirty three patients with idiopathic...

Ataxic dysarthria.

Although ataxic dysarthria has been studied with various methods in several languages, questions remain concerning which features of the disorder are most consistent, which speaking tasks are most sensitive to the disorder, and whether the different speech production subsystems are uniformly affected. Perceptual and acoustic data were obtained from 14 individuals (seven men, seven women) with ataxic dysarthria for several speaking tasks, including sustained vowel phonation, syllable repetition, sentence recitation, and conversation. Multidimensional acoustic analyses of sustained vowel phonation showed that the largest and most frequent abnormality for both men and women was a long-term variability of fundamental frequency. Other measures with a high frequency of abnormality were shimmer and peak amplitude variation (for both sexes) and jitter (for women). Syllable alternating motion rate (AMR) was typically slow and irregular in its temporal pattern. In addition, the energy maxima and minima often were highly variable across repeated syllables, and this variability is thought to reflect poorly coordinated respiratory function and inadequate articulatory/voicing control. Syllable rates tended to be slower for sentence recitation and conversation than for AMR, but the three rates were highly similar. Formant-frequency ranges during sentence production were essentially normal, showing that articulatory hypometria is not a pervasive problem. Conversational samples varied considerably across subjects in intelligibility and number of words/ morphemes in a breath group. Qualitative analyses of unintelligible episodes in conversation showed that these samples generally had a fairly well-defined syllable pattern but subjects differed in the degree to which the acoustic contrasts typical of consonant and vowel sequences were maintained. For some individuals, an intelligibility deficit occurred in the face of highly distinctive (and contrastive) acoustic patterns.

Short-latency changes in voice F0 and neck surface EMG induced by mechanical perturbations of the larynx during sustained vowel phonation.

Nineteen healthy young adult males with normal voice and speech attempted to sustain the vowel /u/ at a constant pitch (target: 180 Hz) and a constant and comfortable loudness level while receiving a sudden mechanical perturbation to the larynx (thyroid prominence) via a servo-controlled probe. The probe moved toward or away from the larynx in a ramp-and-hold fashion (3.3-mm displacement, 0.7 N force, 20-ms rise time, 250-ms duration) as the subjects attempted to maintain a constant probe-larynx pressure. Eighty stimuli were applied in each direction, one stimulus per phonation. Pairs of surface electromyography (EMG) electrodes were attached to the skin of the anterior neck over laryngeal, infralaryngeal, and supralaryngeal areas. The rectified EMG signals, the voltage analog of the voice fundamental frequency (VAF0), and the voltage analog of the probe displacement were digitized and signal-averaged relative to the onset of the stimulus. Sudden perturbation of the larynx induced an instantaneous decrease or increase in VAF0, depending on the direction of the probe's movement, and a short-latency increase in the EMG (30-35 ms) and VAF0 (55-65 ms). We argue that the instantaneous VAF0 change was related to a mechanical effect, and the short-latency VAF0 and EMG changes to reflexogenic effects-the latter most likely associated with both intrinsic and extrinsic laryngeal sensorimotor mechanisms. Further physiological studies are needed to elucidate the sources of the VAF0 and EMG responses. Once elucidated, the present method may provide a powerful noninvasive tool for studying laryngeal neurophysiology. The theoretical and clinical implications of the present findings are addressed.

Botulinum toxin injections for essential voice tremor.

Fifteen patients, 13 women and 2 men, with a mean age of 72.7 years (56 to 86 years) and a clinical diagnosis of essential voice tremor, were treated with botulinum injections to the thyroarytenoid muscles, and in some cases, to the cricothyroid or thyrohyoid muscles. Evaluations were based on subjective judgments by the patients, and on perceptual and acoustic analysis of voice recordings. Subjective evaluations indicated that the treatment had a beneficial effect in 67% of the patients. Perceptual evaluations showed a significant decrease in voice tremor during connected speech (p < .05). Acoustic analysis showed a nearly significant decrease in the fundamental frequency variations (p = .06) and a significant decrease in fundamental frequency during sustained vowel phonation (p < .01 ). The results of perceptual evaluation coincided most closely with the subjective judgments. It was concluded that the treatment was successful in 50% to 65% of the patients, depending on the method of evaluation.

Acoustic and airflow spectral analysis of voice tremor.

Acoustic spectral analysis has been used to describe voice tremor with some success, but no feature distinguishing pathological from normal tremor has been clearly identified. To assist in monitoring voice tremor associated with neurological diseases, objective and quantifiable measures that can distinguish between normal and pathological tremor are desired. This study explored the plausibility of using airflow and acoustic signals to quantify the frequency and amplitude of voice tremor and potentially to distinguish pathological from normal tremor. Subjects were 10 individuals with pathological tremor, most of them individuals with Parkinson's disease, and 10 gender and age-matched individuals with no voice disorder. Simultaneous acoustic and airflow signals were recorded during sustained vowel phonation. The acoustic intensity contours and the airflow signals were submitted to spectral analysis. A peak prominence ratio, defined as the ratio of the spectral peak energy to the overall signal energy, was calculated for each spectral peak below 30 Hz. For each subject, the 6 spectral peaks with the highest peak prominence ratios were selected. Frequency values of the 6 selected acoustic or airflow spectral peaks failed to distinguish tremor group from control group. Peak prominence ratios of the 6 selected acoustic spectral peaks were significantly higher for tremor group than for control group. Although spectral analysis of airflow signals was not useful in differentiating tremor group from control group, acoustic intensity contours and airflow time waveforms were highly and positively correlated in more tremor subjects (90%) than control subjects (40%). This finding suggests that the relationship between acoustic intensity contours and airflow time waveforms may reflect the presence and the source of voice tremor.

A Speaking Task Analysis of the Dysarthria in Cerebellar Disease

Cerebellar disease affects a number of skilled movements, including those in speech. Ataxic dysarthria, the speech disorder that typically accompanies cerebellar disease, was studied by acoustic methods. Control subjects and subjects with ataxic dysarthria were recorded while performing a number of speaking tasks, including sustained vowel phonation, syllable repetition, monosyllabic word production (intelligibility test), sentence recitation, and conversation. Acoustic data derived from the speech samples confirmed the hypothesis that temporal dysregulation is a primary component of the speech disorder. The data also show that the nature of the disorder varies with the speaking task. This result agrees with observations on other motor systems in subjects with cerebellar disease and may be evidence of a dissociation of impairments. Suggestions are offered on the selection of measures for a given task and on the role of the cerebellum in the regulation of speaking.

Acoustic and perceptual characteristics of the voices of sedentary and physically active elderly speakers

The purpose of this study was to investigate perceptual and acoustic characteristics of the voices of physically active and sedentary elderly speakers. Recordings of sustained phonations of the vowel /a/ were obtained from 31 male and female elderly speakers. Twenty adult listeners judged the chronological ages of the elderly speakers from their oral performance. The acoustic parameters of Fo, Fo standard deviation, jitter per cent, shimmer per cent, shimmer in dB and noise-harmonic ratio were measured from the sustained vowel phonations of the elderly speakers. Results indicated that physically active elderly speakers were judged as chronologically younger, had less jitter per cent and Fo standard deviation, than their sedentary cohorts. The results of this study demonstrate the importance of defining laryngeal aging physiologically as well as chronologically.