Auditory Feedback Control of Vocal Pitch in Spasmodic Dysphonia

Influence of Voice Focus on Auditory Feedback Control of Speech Using Long-Term Average Spectrum, Phon Spectrum, and Accelerometry

PURPOSE

This study investigates the effect of voice-focus adjustments on oronasal balance and auditory feedback control of speech via analyzing spectral distribution, perceived loudness, and nasal vibrations during sustained phonation and passage reading.

METHOD

Twenty-five speech-language pathologists sustained /a/ and read passages with forward, backward, and natural voice focuses in quiet and noisy conditions. The low-frequency power (LFP) below 3 Hz of vocal fundamental frequency was analyzed to access audio-vocal feedback control. Long-term average spectra of speech were converted to phon spectra based on equal-loudness contours ISO 226:2003 to estimate perceived loudness of self-voice across different conditions. Nasal vibrations were also recorded using a digital accelerometer to measure oronasal coupling.

RESULTS

Forward-focused voice enhanced the nasal acceleration and reduced LFP, suggesting that increasing the degree of oronasal coupling can improve audio-vocal feedback control compared to natural and backward-focused voices. Voice-focus adjustments were most related to average power and phon values in the 0.2- to 0.3-kHz band. In noise, perceived loudness in the 0.5- to 2.3-kHz band effectively predicted LFP, outperforming the average spectral power of the same band.

CONCLUSIONS

Voice-focus adjustments significantly impact both the acoustic transfer function of the vocal tract and the spontaneous fine-tuning of audio-vocal integration. This influence becomes particularly pronounced when sound intensity or perceived loudness is changed within the frequency range of 0.2-2.3 kHz, depending on the voice focus selected by the speakers.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.27183483.

Patient Motivation for Voice Therapy Increases After Stimulability Testing: Validation of a Voice Therapy Motivation and Voice Perception Inventory

OBJECTIVE

Measuring patient motivation for voice therapy is an important component of determining prognosis and estimating compliance. Voice stimulability testing is assumed to influence the patient's motivation by improving their perception of the sound and/or feel of the voice. The purpose of this study was to validate a Voice Therapy Motivation and Voice Perception Inventory and to determine whether stimulability testing elicits improvements in motivation and patient-perceived voice status.

METHOD

Seventy-five patients who underwent initial voice therapy evaluation completed a four-item inventory that queried their commitment to voice therapy, confidence that they could change their voice through voice therapy, perception of their voice severity, and ratings of their vocal effort. Inventories were completed shortly before and after stimulability testing. A psychometric analysis of the survey was conducted, including the internal consistency of each construct of the inventory along with content, predictive, and concurrent validity. Paired-samples statistical analyses were conducted to determine differences before and after stimulability testing, and Spearman correlations between voice and motivation ratings were conducted to determine relationships between the patient's perception of their voice and their motivation for voice therapy.

RESULTS

Internal consistency reliability was acceptable to good for each construct, particularly after stimulability testing. Motivation scales were predictive of returning for voice therapy sessions, subjective improvement of voice by the first therapy session, and likelihood of the patient practicing the home practice program. Patient ratings of voice severity and effort were positively correlated with clinician ratings of overall severity. Motivation and voice impairment perception improved following stimulability testing. Reduction in vocal effort was related to improved motivation, but change in voice severity was not.

CONCLUSIONS

Voice stimulability testing can influence patient motivation for voice therapy and patient-perceived voice improvements. It should be considered a critical part of the voice evaluation.

"Lombard Effect" and Voice Changes in Adductor Laryngeal Dystonia: A Pilot Study

OBJECTIVES

The aim was to describe the acoustic, auditory-perceptive, and subjective voice changes under the Lombard effect (LE) in adductor laryngeal dystonia (AdLD) patients.

METHODS

Subjective perception of vocal effort (OMNI Vocal Effort Scale OMNI-VES), Maximum Phonation Time (MPT), and the perceptual severity of dysphonia (GRBAS scale) were assessed in condition of stillness and under LE in 10 AdLD patients and in 10 patients with typical voice. Speakers were asked to produce the sustained vowel /a/ and to read a phonetically balanced text aloud. Using the PRAAT software, the following acoustic parameters were analyzed: Mean Pitch (Hz), Minimum and Maximum Intensity (dB), the Fraction of Locally Unvoiced Frames, the Number of Voice Breaks, the Degree of Voice Breaks (%), the Cepstral Peak Prominence-Smoothed (CPPS) (dB).

RESULTS

Under LE, the AdLD group showed a decrease of both G and S parameters of GRBAS and subjective effort, mean MPT increased significantly; in the controls there were no significant changes. In both groups under LE, pitch and intensity of the sustained vowel /a/ significantly increased consistently with LE. In the AdLD group the mean gain of OMNI-VES score and the mean gain of each parameter of the speech analysis were significantly greater than the controls' ones.

CONCLUSION

Auditory feedback deprivation obtained under LE improves subjective, perceptual-auditory, and acoustics parameters of AdLD patients. These findings encourage further research to provide new knowledge into the role of the auditory system in the pathogenesis of AdLD and to develop new therapeutic strategies.

LEVEL OF EVIDENCE

4 Laryngoscope, 134:3754-3760, 2024.

Sensorimotor Integration in Patients with Voice Disorders: A Scoping Review of Behavioral Research

BACKGROUND

In recent years, research has determined that impaired sensorimotor integration is a contributor to the formation of voice symptoms and voice disorders. A scoping review is undertaken to explore the current state of scientific research regarding behavioral examinations of sensorimotor integration impairments in patients.

SUMMARY

Following the guidelines of the PRISMA Extension for Scoping Reviews, five online databases identified papers published between 2000 and 2023, from which 17 publications were selected that used sensorimotor integration paradigms with voice-related acoustics as an outcome variable in individuals diagnosed with a voice disorder. Across the 17 studies, sensorimotor integration was behaviorally examined via auditory-motor paradigms in 315 patients with voice disorders and 344 controls. Broadly, patients with vocal hyperfunction demonstrated impaired auditory-motor and somatosensory-motor integration. Patients with unilateral vocal fold paralysis demonstrated impaired sensorimotor integration attributed to changes in the primary brain areas of speech motor control. Patients with laryngeal dystonia demonstrated varying results, with no conclusive evidence regarding sensorimotor integration in behavioral voicing tasks. Patients with Parkinson's disease demonstrated varying results as well, with a general trend of increased dependance on the feedback control system of voice production. Patients with ataxic dysarthria demonstrated that auditory feedback control was impaired possibly due to inaccurate error estimation and correction arising from the damage to their cerebellar pathways. Finally, patients with cerebellar degeneration demonstrated disruptions in both feedback and feed-forward control.

KEY MESSAGES

Sensorimotor integration in the context of voice disorders is an important consideration in understanding how different sensory streams operate in healthy voice production, and how sensory feedback can be optimized in clinical treatments of voice disorders. The present scoping review reveals that behavioral research has focused primarily on auditory-motor integration paradigms, and this supports the possibility of a disconnect between these behavioral studies and existing theoretical conceptualizations of vocal motor control.

Voice Biofeedback via Bone Conduction Headphones: Effects on Acoustic Voice Parameters and Self-Reported Vocal Effort in Individuals With Voice Disorders

PURPOSE

This study explores sidetone amplification (amplified playback of one's own voice) provided via bone conduction in participants with voice disorders. The effects of bone conduction feedback on acoustic voice parameters and vocal effort ratings are examined.

METHODS

Speech samples of 47 participants with voice disorders were recorded in three auditory feedback conditions: two with sidetone amplification delivered via bone conduction and one condition with no alteration of the feedback. After each task, the participants rated their vocal effort on a visual analog scale. The voice recordings were evaluated by a speech-language pathologist through the GRBAS scale and processed to calculate the within-participant centered sound pressure level (SPL) values, the mean pitch strength (PS), the time dose (Dt%), and cepstral peak prominence smoothed (CPPS). The effects of the feedback conditions on these acoustic parameters and vocal effort ratings were analyzed.

RESULTS

The high sidetone amplification condition resulted in a statistically significant decrease in the within-participant centered SPL values and mean pitch strength across all participants. The feedback conditions had no statistically significant effects on the vocal effort ratings, time dose (Dt%), or CPPS.

CONCLUSIONS

This study provides an evidence that bone conduction sidetone amplification contributes to a consistent adaptation in the within-participant centered SPL values (ΔSPL) in patients with vocal hyperfunction, glottal insufficiency, and organic/neurological laryngeal pathologies compared to conditions with no feedback.

What Can Altered Auditory Feedback Paradigms Tell Us About Vocal Motor Control in Individuals With Voice Disorders?

Purpose

The goal of this review article is to provide a summary of the progression of altered auditory feedback (AAF) as a method to understand the pathophysiology of voice disorders. This review article focuses on populations with voice disorders that have thus far been studied using AAF, including individuals with Parkinson's disease, cerebellar degeneration, hyperfunctional voice disorders, vocal fold paralysis, and laryngeal dystonia. Studies using AAF have found that individuals with Parkinson's disease, cerebellar degeneration, and laryngeal dystonia have hyperactive auditory feedback responses due to differing underlying causes. In persons with PD, the hyperactivity may be a compensatory mechanism for atypically weak feedforward motor control. In individuals with cerebellar degeneration and laryngeal dystonia, the reasons for hyperactivity remain unknown. Individuals with hyperfunctional voice disorders may have auditory-motor integration deficits, suggesting atypical updating of feedforward motor control.

Conclusions

These findings have the potential to provide critical insights to clinicians in selecting the most effective therapy techniques for individuals with voice disorders. Future collaboration between clinicians and researchers with the shared objective of improving AAF as an ecologically feasible and valid tool for clinical assessment may provide more personalized therapy targets for individuals with voice disorders.

Temporal specificity of abnormal neural oscillations during phonatory events in laryngeal dystonia

Laryngeal dystonia is a debilitating disorder of voicing in which the laryngeal muscles are intermittently in spasm resulting in involuntary interruptions during speech. The central pathophysiology of laryngeal dystonia, underlying computational impairments in vocal motor control, remains poorly understood. Although prior imaging studies have found aberrant activity in the CNS during phonation in patients with laryngeal dystonia, it is not known at what timepoints during phonation these abnormalities emerge and what function may be impaired. To investigate this question, we recruited 22 adductor laryngeal dystonia patients (15 female, age range = 28.83-72.46 years) and 18 controls (eight female, age range = 27.40-71.34 years). We leveraged the fine temporal resolution of magnetoencephalography to monitor neural activity around glottal movement onset, subsequent voice onset and after the onset of pitch feedback perturbations. We examined event-related beta-band (12-30 Hz) and high-gamma-band (65-150 Hz) neural oscillations. Prior to glottal movement onset, we observed abnormal frontoparietal motor preparatory activity. After glottal movement onset, we observed abnormal activity in the somatosensory cortex persisting through voice onset. Prior to voice onset and continuing after, we also observed abnormal activity in the auditory cortex and the cerebellum. After pitch feedback perturbation onset, we observed no differences between controls and patients in their behavioural responses to the perturbation. But in patients, we did find abnormal activity in brain regions thought to be involved in the auditory feedback control of vocal pitch (premotor, motor, somatosensory and auditory cortices). Our study results confirm the abnormal processing of somatosensory feedback that has been seen in other studies. However, there were several remarkable findings in our study. First, patients have impaired vocal motor activity even before glottal movement onset, suggesting abnormal movement preparation. These results are significant because (i) they occur before movement onset, abnormalities in patients cannot be ascribed to deficits in vocal performance and (ii) they show that neural abnormalities in laryngeal dystonia are more than just abnormal responses to sensory feedback during phonation as has been hypothesized in some previous studies. Second, abnormal auditory cortical activity in patients begins even before voice onset, suggesting abnormalities in setting up auditory predictions before the arrival of auditory feedback at voice onset. Generally, activation abnormalities identified in key brain regions within the speech motor network around various phonation events not only provide temporal specificity to neuroimaging phenotypes in laryngeal dystonia but also may serve as potential therapeutic targets for neuromodulation.

Pitch Discrimination Testing in Patients with a Voice Disorder

Auditory perception plays an important role in voice control. Pitch discrimination (PD) is a key index of auditory perception and is influenced by a variety of factors. Little is known about the potential effects of voice disorders on PD and whether PD testing can differentiate people with and without a voice disorder. We thus evaluated PD in a voice-disordered group (n = 71) and a non-voice-disordered control group (n = 80). The voice disorders included muscle tension dysphonia and neurological voice disorders and all participants underwent PD testing as part of a comprehensive voice assessment. Percentage of accurate responses and PD threshold were compared across groups. The PD percentage accuracy was significantly lower in the voice-disordered group than the control group, irrespective of musical background. Participants with voice disorders also required a larger PD threshold to correctly discriminate pitch differences. The mean PD threshold significantly discriminated the voice-disordered groups from the control group. These results have implications for the voice control and pathogenesis of voice disorders. They support the inclusion of PD testing during comprehensive voice assessment and throughout the treatment process for patients with voice disorders.