Distinct neural systems recruited when speech production is modulated by different masking sounds

Influences of speaking task demands on sensorimotor oscillations in adults who stutter: Implications for speech motor control

OBJECTIVE

Motivated by previous inconsistent findings, this study aims to improve understanding of sensorimotor beta (β; 15-30 Hz) and alpha (α; 8-14 Hz) speech-related power differences between stuttering and non-stuttering adults.

METHODS

Electroencephalography was recorded as adults who stutter (AWS) and matched fluent controls answered questions in Quiet and Informational Masked backgrounds. Bilateral sensorimotor β and α power during speech planning and execution were measured from mu (μ) rhythm components.

RESULTS

Compared to controls, AWS exhibited reduced left hemisphere β and α power in both speaking conditions during speech planning and execution. AWS displayed reduced left α power in the Informational Masking compared to Quiet. Within AWS β and α power, which were tightly coupled, oppositely predicted stuttering severity and β-α dissociation (β minus α) was the strongest predictor.

CONCLUSION

Neither β nor α power are reliable markers of speech motor stability due to their sensitivity to speech task automaticity. However, relationships between these two sensorimotor rhythms warrant further investigation for understanding motor control.

SIGNIFICANCE

Data help explain previous mixed findings in reference to extant models of speech motor control in stuttering and may have clinical implications for developing neurostimulation protocols targeting improved speech fluency.

"Competing Noises": How Background Noise Impacts the Communication Experiences of People With Mild-to-Moderate Aphasia

PURPOSE

The aim of this study was to explore the subjective experiences of people with aphasia when communicating in the presence of various types of background noise. We hypothesized that (a) people with aphasia would report greater perceived effort and stress than controls when talking in noise, (b) perceived effort and stress would be greater in noise than silence, and (c) people with aphasia would describe more negative reactions to communicating in noise than controls.

METHOD

Eleven people with aphasia and 11 age- and gender-matched controls retold stories in a baseline silent condition and five background noise conditions (pink noise, cocktail party, monologue, one-sided phone call, and conversation) and rated their perceived effort and stress after each story. Participants then described their experience in a semistructured interview. Perceived effort and stress ratings were analyzed statistically using quantitative methods. Interview data were analyzed qualitatively.

RESULTS

Quantitative findings showed that people with aphasia reported significantly greater perceived effort and stress than controls. Across groups, phone call, conversation, and monologue conditions were perceived as either more effortful or stressful than the silent baseline condition. Although both participant groups discussed cognitive and emotional challenges and strategies related to talking in noise, qualitative findings showed distinct difficulties for people with aphasia. Specifically, unlike controls, participants with aphasia mentioned difficulty ignoring background noise, decreased processing speed, fatigue, negative emotional reactions, deliberately focusing, slowing down/taking breaks, and consciously regulating their emotions.

CONCLUSIONS

Although aphasia therapy often occurs in quiet clinic environments, everyday communication does not. The increased perceived difficulty that people with aphasia have for coping with background noise should be acknowledged, and training should be designed to prepare people with aphasia to communicate in noisy environments.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.27893445.

Modeling voice production and self-perception in noise: Understanding the Lombard effect in non-phonotraumatic vocal hyperfunctiona)

The sensorimotor adaptation process is crucial for maintaining oral communication. Recent studies have shown that individuals with non-phonotraumatic vocal hyperfunction (NPVH) experience difficulties in sensorimotor adaptation when speaking in noise (known as the Lombard effect). However, the role of auditory and somatosensory feedback in the dynamics of adaptation to speaking in noise is still unclear. In this study, the use of a simple three-parameter mathematical model, known as SimpleDIVA model, was extended to explore the adaptation dynamics of speaking in noise among a group of participants with typical voices and NPVH. All participants were asked to utter a series of syllables under three conditions: baseline (quiet environment), Lombard (speech-shaped noise at 80 dB), and recovery (quiet environment after 5 min of rest). The results indicate that participants with NPVH did not return to baseline after exposure to speaking under noise. The SimpleDIVA model analysis reveals a diminished feedforward learning rate and reduced somatosensory feedback gain in participants with NPVH in comparison to participants with typical voices. This suggests that participants with NPVH may be using less somatosensory information when speaking in noise and may require more time to update the feedforward commands during and after speaking in noise.

Too loud to hear myself think: deleterious effects of noise in the operating room

Noise is part of daily life in the operating room, and too often is viewed as a necessary evil. However, much of the noise in operating rooms (ORs) is unnecessary, such as extraneous conversations and music, and could be reduced. At the least, noise is known to increase staff stress and to hamper effective communication; at the worst, it adversely affects patient outcomes. Every member of the OR team should be cognisant of this and work to reduce unnecessary noise.

Telling Stories in Noise: The Impact of Background Noises on Spoken Language for People With Aphasia

PURPOSE

The purpose of this study was to determine how different background noise conditions affect the spoken language of participants with aphasia during a story retell task.

METHOD

Participants included 11 adults with mild to moderate aphasia and 11 age- and gender-matched controls. Participants retold stories in a silent baseline and five background noise conditions (conversation, monologue, phone call, cocktail, and pink noise). Dependent measures of speech acoustics (fundamental frequency and mean intensity), speech fluency (speech rate and disfluent words), and language production (correct information units [CIUs], lexical errors, lexical diversity, and cohesive utterances) were compared between groups and across conditions.

RESULTS

Background noise resulted in higher fundamental frequency (fo) and increased mean intensity for control participants across all noise conditions but only across some conditions for participants with aphasia. In relation to language production, background noise interfered significantly more with communication efficiency (i.e., percent CIUs) for participants with aphasia than the control group. For participants with aphasia, the phone call condition led to decreased lexical diversity. Across groups, condition effects generally suggested more interference on speech acoustics in conditions where continuous noise was present and more interference on language in conditions that presented continuous informational noise.

CONCLUSIONS

Although additional research is needed, preliminary findings suggest that background noise interferes with narrative discourse more for people with aphasia (PWA) than neurologically healthy adults. PWA may benefit from therapy that directly addresses communicating in noise.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.23681703.

Lombard Effect in Individuals With Nonphonotraumatic Vocal Hyperfunction: Impact on Acoustic, Aerodynamic, and Vocal Fold Vibratory Parameters

PURPOSE

This exploratory study aims to investigate variations in voice production in the presence of background noise (Lombard effect) in individuals with nonphonotraumatic vocal hyperfunction (NPVH) and individuals with typical voices using acoustic, aerodynamic, and vocal fold vibratory measures of phonatory function.

METHOD

Nineteen participants with NPVH and 19 participants with typical voices produced simple vocal tasks in three sequential background conditions: baseline (in quiet), Lombard (in noise), and recovery (5 min after removing the noise). The Lombard condition consisted of speech-shaped noise at 80 dB SPL through audiometric headphones. Acoustic measures from a microphone, glottal aerodynamic parameters estimated from the oral airflow measured with a circumferentially vented pneumotachograph mask, and vocal fold vibratory parameters from high-speed videoendoscopy were analyzed.

RESULTS

During the Lombard condition, both groups exhibited a decrease in open quotient and increases in sound pressure level, peak-to-peak glottal airflow, maximum flow declination rate, and subglottal pressure. During the recovery condition, the acoustic and aerodynamic measures of individuals with typical voices returned to those of the baseline condition; however, recovery measures for individuals with NPVH did not return to baseline values.

CONCLUSIONS

As expected, individuals with NPVH and participants with typical voices exhibited a Lombard effect in the presence of elevated background noise levels. During the recovery condition, individuals with NPVH did not return to their baseline state, pointing to a persistence of the Lombard effect after noise removal. This behavior could be related to disruptions in laryngeal motor control and may play a role in the etiology of NPVH.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.20415600.

The combined effects of contextual predictability and noise on the acoustic realisation of German syllables

Speakers tend to speak clearly in noisy environments, while they tend to reserve effort by shortening word duration in predictable contexts. It is unclear how these two communicative demands are met. The current study investigates the acoustic realizations of syllables in predictable vs unpredictable contexts across different background noise levels. Thirty-eight German native speakers produced 60 CV syllables in two predictability contexts in three noise conditions (reference = quiet, 0 dB and -10 dB signal-to-noise ratio). Duration, intensity (average and range), F0 (median), and vowel formants of the target syllables were analysed. The presence of noise yielded significantly longer duration, higher average intensity, larger intensity range, and higher F0. Noise levels affected intensity (average and range) and F0. Low predictability syllables exhibited longer duration and larger intensity range. However, no interaction was found between noise and predictability. This suggests that noise-related modifications might be independent of predictability-related changes, with implications for including channel-based and message-based formulations in speech production.

The effects of a simulated fMRI environment on voice intensity in individuals with Parkinson's disease hypophonia and older healthy adults

PURPOSE

Functional magnetic resonance imaging (fMRI) has promise for understanding neural mechanisms of neurogenic speech and voice disorders. However, performing vocal tasks within the fMRI environment may not always be analogous to performance outside of the scanner. Using a mock MRI scanner, this study examines the effects of a simulated scanning environment on vowel intensity in individuals with Parkinson's disease (PD) and hypophonia and older healthy control (OHC) participants.

METHOD

Thirty participants (15 PD, 15 OHC) performed a sustained /ɑ/ vowel production task in three conditions: 1) Upright, 2) Mock Scanner + No Noise, and 3) Mock Scanner + MRI noise. We used a linear mixed-effects (multi-level) model to evaluate the contributions of group and recording environment to vowel intensity. A second linear mixed-effects model was also used to evaluate the contributions of PD medication state (On vs. Off) to voice intensity.

RESULTS

Vowel intensity was significantly lower for PD compared to the OHC group. The intensity of vowels produced in the Upright condition was significantly lower compared to the Mock Scanner + No Noise condition, while vowel intensity in the Mock Scanner + MRI Noise condition was significantly higher compared to the Mock Scanner + No Noise condition. A group by condition interaction also indicated that the addition of scanner noise had a greater impact on the PD group. A second analysis conducted within the PD group showed no effects of medication state on vowel intensity.

CONCLUSION

Our findings demonstrate that performance on voice production tasks is altered for PD and OHC groups when translated into the fMRI environment, even in the absence of acoustic scanner noise. For fMRI studies of voice in PD hypophonia, careful thought should be given to how the presence of acoustic noise may differentially affect PD and OHC, for both group and task comparisons.

Effects of Background Noise on Speech and Language in Young Adults

Purpose The aim of this study was to investigate how different types of background noise that differ in their level of linguistic content affect speech acoustics, speech fluency, and language production for young adult speakers when performing a monologue discourse task. Method Forty young adults monologued by responding to open-ended questions in a silent baseline and five background noise conditions (debate, movie dialogue, contemporary music, classical music, and pink noise). Measures related to speech acoustics (intensity and frequency), speech fluency (speech rate, pausing, and disfluencies), and language production (lexical, morphosyntactic, and macrolinguistic structure) were analyzed and compared across conditions. Participants also reported on which conditions they perceived as more distracting. Results All noise conditions resulted in some change to spoken language compared with the silent baseline. Effects on speech acoustics were consistent with expected changes due to the Lombard effect (e.g., increased intensity and fundamental frequency). Effects on speech fluency showed decreased pausing and increased disfluencies. Several background noise conditions also seemed to interfere with language production. Conclusions Findings suggest that young adults present with both compensatory and interference effects when speaking in noise. Several adjustments may facilitate intelligibility when noise is present and help both speaker and listener maintain attention on the production. Other adjustments provide evidence that background noise eliciting linguistic interference has the potential to degrade spoken language even for healthy young adults, because of increased cognitive demands.

Processing of Degraded Speech in Brain Disorders

The speech we hear every day is typically "degraded" by competing sounds and the idiosyncratic vocal characteristics of individual speakers. While the comprehension of "degraded" speech is normally automatic, it depends on dynamic and adaptive processing across distributed neural networks. This presents the brain with an immense computational challenge, making degraded speech processing vulnerable to a range of brain disorders. Therefore, it is likely to be a sensitive marker of neural circuit dysfunction and an index of retained neural plasticity. Considering experimental methods for studying degraded speech and factors that affect its processing in healthy individuals, we review the evidence for altered degraded speech processing in major neurodegenerative diseases, traumatic brain injury and stroke. We develop a predictive coding framework for understanding deficits of degraded speech processing in these disorders, focussing on the "language-led dementias"-the primary progressive aphasias. We conclude by considering prospects for using degraded speech as a probe of language network pathophysiology, a diagnostic tool and a target for therapeutic intervention.

Error in the Superior Temporal Gyrus? A Systematic Review and Activation Likelihood Estimation Meta-Analysis of Speech Production Studies

Evidence for perceptual processing in models of speech production is often drawn from investigations in which the sound of a talker's voice is altered in real time to induce "errors." Methods of acoustic manipulation vary but are assumed to engage the same neural network and psychological processes. This paper aims to review fMRI and PET studies of altered auditory feedback and assess the strength of the evidence these studies provide for a speech error correction mechanism. Studies included were functional neuroimaging studies of speech production in neurotypical adult humans, using natural speech errors or one of three predefined speech manipulation techniques (frequency altered feedback, delayed auditory feedback, and masked auditory feedback). Seventeen studies met the inclusion criteria. In a systematic review, we evaluated whether each study (1) used an ecologically valid speech production task, (2) controlled for auditory activation caused by hearing the perturbation, (3) statistically controlled for multiple comparisons, and (4) measured behavioral compensation correlating with perturbation. None of the studies met all four criteria. We then conducted an activation likelihood estimation meta-analysis of brain coordinates from 16 studies that reported brain responses to manipulated over unmanipulated speech feedback, using the GingerALE toolbox. These foci clustered in bilateral superior temporal gyri, anterior to cortical fields typically linked to error correction. Within the limits of our analysis, we conclude that existing neuroimaging evidence is insufficient to determine whether error monitoring occurs in the posterior superior temporal gyrus regions proposed by models of speech production.

Understanding rostral-caudal auditory cortex contributions to auditory perception

There are functional and anatomical distinctions between the neural systems involved in the recognition of sounds in the environment and those involved in the sensorimotor guidance of sound production and the spatial processing of sound. Evidence for the separation of these processes has historically come from disparate literatures on the perception and production of speech, music and other sounds. More recent evidence indicates that there are computational distinctions between the rostral and caudal primate auditory cortex that may underlie functional differences in auditory processing. These functional differences may originate from differences in the response times and temporal profiles of neurons in the rostral and caudal auditory cortex, suggesting that computational accounts of primate auditory pathways should focus on the implications of these temporal response differences.