Investigation of Embodied Language Processing on Command-Swallow Performance in Healthy Participants.

Purpose During videofluoroscopic examination of swallowing, patients commonly are instructed to hold a bolus in their mouth until they hear a verbal instruction to swallow, which usually consists of the word swallow and is commonly referred to as the command swallow condition. The language-induced motor facilitation theory suggests that linguistic processes associated with the verbal command to swallow should facilitate the voluntary component of swallowing. As such, the purpose of the study was to examine the linguistic influences of the verbal command on swallowing. Method Twenty healthy young adult participants held a 5-ml liquid bolus in their mouth and swallowed the bolus after hearing one of five acoustic stimuli presented randomly: congruent action word (swallow), incongruent action word (cough), congruent pseudoword (spallow), incongruent pseudoword (pough), and nonverbal stimulus (1000-Hz pure tone). Suprahyoid muscle activity during swallowing was measured via surface electromyography (sEMG). Results The onset and peak sEMG latencies following the congruent action word swallow were shorter than latencies following the pure tone and pseudowords but were not different from the incongruent action word. The lack of difference between swallow and cough did not negate the positive impact of real words on timing. In contrast to expectations, sEMG activity duration and rise time were longer following the word swallow than the pure tone and pseudowords but were not different from cough. No differences were observed for peak suprahyoid muscle activity amplitude and fall times. Conclusions Language facilitation was observed in swallowing. The clinical utility of the information obtained in the study may depend on the purposes for using the command swallow and the type of patient being assessed. However, linguistic processing under the command swallow condition may alter swallow behaviors and suggests that linguistic inducement could be useful as a compensatory technique for patients with difficulty initiating oropharyngeal swallows.

Subthalamic Nucleus and Sensorimotor Cortex Activity During Speech Production.

The sensorimotor cortex is somatotopically organized to represent the vocal tract articulators such as lips, tongue, larynx, and jaw. How speech and articulatory features are encoded at the subcortical level, however, remains largely unknown. We analyzed LFP recordings from the subthalamic nucleus (STN) and simultaneous electrocorticography recordings from the sensorimotor cortex of 11 human subjects (1 female) with Parkinson's disease during implantation of deep-brain stimulation (DBS) electrodes while they read aloud three-phoneme words. The initial phonemes involved either articulation primarily with the tongue (coronal consonants) or the lips (labial consonants). We observed significant increases in high-gamma (60-150 Hz) power in both the STN and the sensorimotor cortex that began before speech onset and persisted for the duration of speech articulation. As expected from previous reports, in the sensorimotor cortex, the primary articulators involved in the production of the initial consonants were topographically represented by high-gamma activity. We found that STN high-gamma activity also demonstrated specificity for the primary articulator, although no clear topography was observed. In general, subthalamic high-gamma activity varied along the ventral-dorsal trajectory of the electrodes, with greater high-gamma power recorded in the dorsal locations of the STN. Interestingly, the majority of significant articulator-discriminative activity in the STN occurred before that in sensorimotor cortex. These results demonstrate that articulator-specific speech information is contained within high-gamma activity of the STN, but with different spatial and temporal organization compared with similar information encoded in the sensorimotor cortex.SIGNIFICANCE STATEMENT Clinical and electrophysiological evidence suggest that the subthalamic nucleus (STN) is involved in speech; however, this important basal ganglia node is ignored in current models of speech production. We previously showed that STN neurons differentially encode early and late aspects of speech production, but no previous studies have examined subthalamic functional organization for speech articulators. Using simultaneous LFP recordings from the sensorimotor cortex and the STN in patients with Parkinson's disease undergoing deep-brain stimulation surgery, we discovered that STN high-gamma activity tracks speech production at the level of vocal tract articulators before the onset of vocalization and often before related cortical encoding.

Perceptual Clinical Features in Exercise-Induced Laryngeal Obstruction (EILO): Toward Improved Diagnostic Approaches.

INTRODUCTION: Athletes with exercise-induced laryngeal obstruction (EILO) (previously commonly referred to as paradoxical vocal fold motion disorder, or paradoxical vocal fold motion, among other terms) are often misdiagnosed, resulting in prolonged, and at times inappropriate, clinical management. The high prevalence of misdiagnosis is largely due to a lack of universal consensus of key clinical features indicating EILO and a dearth of validated quantitative approaches to accurately detect episodic laryngeal breathing disorders (ELBD) from other pathologies. Additionally, mechanisms underlying EILO clinical presentation are poorly understood, further confounding identification and management of the condition. Therefore, the objectives of this study were twofold. The first was to identify patient-centered perception of symptoms that could distinguish adolescent athletes with EILO from athletes without the condition, at baseline (rest) and during an exercise challenge (provocation), and to quantify symptom severities for use as preliminary diagnostic benchmarks. The second objective was to investigate the merit of one commonly proposed mechanism in the EILO literature-stress reactivity (temperament)-by comparing personality traits in athletes with and without EILO. METHODS: Twelve (12) athletes diagnosed with EILO and 14 healthy athletic volunteers without the condition were asked to rate the severity of their present symptoms using a 0-100 continuous visual analog scale. Participants then underwent an exercise challenge with simultaneous laryngoscopy and were asked to complete the same set of symptom severity ratings experienced during rigorous exercise. Finally, participants completed the Fear subscale on the early adolescent temperament questionnaire-revised (EATQ-R) to measure self-perceived levels of stress reactivity. RESULTS: There were significant group differences for inspiratory and expiratory dyspnea with exercise (P = 0.01). Symptoms of stridor (EILO: P = .01; control: P = .001) and throat tightness (EILO: P = .01, control: P = .01) were statistically different between rest and exercise in both groups. However, no group differences were found on these two parameters (P > .05). Other symptoms from the list of previously purported symptoms indicative of ELBD (e.g. cough, dysphonia) were infrequently reported in the exercise variant. Additionally, measurements of stress reactivity on the EATQ-R Fear subscale were similar between the two athletic groups. Interestingly, EATQ-R Fear Subscale scores for both groups were significantly higher compared to typical adolescents in the U.S. population (P < .001, respectively). DISCUSSION: Results suggest dyspnea severity, particularly when experienced during an exercise-induced ELBD (EILO) episode, is the most sensitive symptom parameter to distinguish individuals with EILO from those without the condition. These findings confirm previous literature describing episodic laryngeal breathing disorders in clinical cohorts. Results also showed symptoms of throat tightness and stridor is more prevalent during exercise, compared to rest. However, the level of their severity occurred variably across both groups of athletes and may point to a less robust indication of pathology. Finally, similarities to stress reactivity between the two athletic groups imply certain temperaments historically attributed to patients with EILO may instead better reflect temperaments in competitive young athletes, in general. CONCLUSION: Study findings highlight the importance of using normative comparisons in the study of episodic laryngeal breathing disorders to prevent overgeneralization of characteristics to clinical cohorts. Results also speak of the clinical utility of exercise challenge to improve specificity of EILO diagnosis.

The Study of Laryngoscopic and Autonomic Patterns in Exercise-Induced Laryngeal Obstruction.

OBJECTIVES: (1) Identify laryngeal patterns axiomatic to exercise-induced laryngeal obstruction (EILO) and (2) investigate the role of autonomic function in EILO. METHODS: Twenty-seven athletic adolescents (13 EILO, 14 control) underwent laryngoscopy at rest and exercise. Glottal configurations, supraglottic dynamics, systolic blood pressure responses, and heart rate recovery were compared between conditions and groups. RESULTS: Inspiratory glottal angles were smaller in the EILO group than the control group with exercise. However, group differences were not statistically significant ( P > .05), likely due to high variability of laryngeal responses in the EILO group. Expiratory glottal patterns showed statistically greater abductory responses to exercise in the control group ( P = .001) but not the EILO group ( P > .05). Arytenoid prolapse occurred variably in both groups. Systolic blood pressure responses to exercise were higher in the control group, and heart rate recovery was faster in the EILO group. However, no significant differences were seen between the 2 groups on either autonomic parameter ( P > .05). CONCLUSIONS: "Paradoxical" inspiratory and blunted expiratory vocal fold pattern responses to exercise best characterize EILO. Group differences were only seen with exercise challenge, thus highlighting the utility of provocation and control groups to identify EILO.

Subthalamic Nucleus Neurons Differentially Encode Early and Late Aspects of Speech Production.

Basal ganglia-thalamocortical loops mediate all motor behavior, yet little detail is known about the role of basal ganglia nuclei in speech production. Using intracranial recording during deep brain stimulation surgery in humans with Parkinson's disease, we tested the hypothesis that the firing rate of subthalamic nucleus neurons is modulated in sync with motor execution aspects of speech. Nearly half of 79 unit recordings exhibited firing-rate modulation during a syllable reading task across 12 subjects (male and female). Trial-to-trial timing of changes in subthalamic neuronal activity, relative to cue onset versus production onset, revealed that locking to cue presentation was associated more with units that decreased firing rate, whereas locking to speech onset was associated more with units that increased firing rate. These unique data indicate that subthalamic activity is dynamic during the production of speech, reflecting temporally-dependent inhibition and excitation of separate populations of subthalamic neurons.SIGNIFICANCE STATEMENT The basal ganglia are widely assumed to participate in speech production, yet no prior studies have reported detailed examination of speech-related activity in basal ganglia nuclei. Using microelectrode recordings from the subthalamic nucleus during a single-syllable reading task, in awake humans undergoing deep brain stimulation implantation surgery, we show that the firing rate of subthalamic nucleus neurons is modulated in response to motor execution aspects of speech. These results are the first to establish a role for subthalamic nucleus neurons in encoding of aspects of speech production, and they lay the groundwork for launching a modern subfield to explore basal ganglia function in human speech.

Speaker and Observer Perceptions of Physical Tension during Stuttering.

PURPOSE: Speech-language pathologists routinely assess physical tension during evaluation of those who stutter. If speakers experience tension that is not visible to clinicians, then judgments of severity may be inaccurate. This study addressed this potential discrepancy by comparing judgments of tension by people who stutter and expert clinicians to determine if clinicians could accurately identify the speakers' experience of physical tension. METHOD: Ten adults who stutter were audio-video recorded in two speaking samples. Two board-certified specialists in fluency evaluated the samples using the Stuttering Severity Instrument-4 and a checklist adapted for this study. Speakers rated their tension using the same forms, and then discussed their experiences in a qualitative interview so that themes related to physical tension could be identified. RESULTS: The degree of tension reported by speakers was higher than that observed by specialists. Tension in parts of the body that were less visible to the observer (chest, abdomen, throat) was reported more by speakers than by specialists. The thematic analysis revealed that speakers' experience of tension changes over time and that these changes may be related to speakers' acceptance of stuttering. CONCLUSION: The lack of agreement between speaker and specialist perceptions of tension suggests that using self-reports is a necessary component for supporting the accurate diagnosis of tension in stuttering.

Relationship between tongue positions and formant frequencies in female speakers.

This study examined the relationship (1) between acoustic vowel space and the corresponding tongue kinematic vowel space and (2) between formant frequencies (F1 and F2) and tongue x-y coordinates for the same time sampling point. Thirteen healthy female adults participated in this study. Electromagnetic articulography and synchronized acoustic recordings were utilized to obtain vowel acoustic and tongue kinematic data across ten speech tasks. Intra-speaker analyses showed that for 10 of the 13 speakers the acoustic vowel space was moderately to highly correlated with tongue kinematic vowel space; much weaker correlations were obtained for inter-speaker analyses. Correlations of individual formants with tongue positions showed that F1 varied strongly with tongue position variations in the y dimension, whereas F2 was correlated in equal magnitude with variations in the x and y positions. For within-speaker analyses, the size of the acoustic vowel space is likely to provide a reasonable inference of size of the tongue working space for most speakers; unfortunately there is no a priori, obvious way to identify the speakers for whom the covariation is not significant. A second conclusion is that F1 variations reflect tongue height, but F2 is a much more complex reflection of tongue variation in both dimensions.

Unexpected intensity changes in the ear canal during a F(0)-shifted feedback experiment.

Effects of frequency-shifted feedback are typically examined using Eventide Harmonizer Series processors to shift the fundamental frequency (F0) of auditory feedback during vocalizations, eliciting compensatory shifts in speaker F0. Recently, unexpected intensity changes were observed in speakers' ear canals, corresponding with F0 shifts. An investigation revealed that feedback time delays introduced by the processor resulted in phase shifts between feedback and unprocessed voice signals radiating into the ear canal via bone conduction, producing combination waves with gains as high as 6 dB. Shifts of this magnitude potentially alter the interpretation of previously published results and should be controlled in future studies.

Effects of prosody and position on the timing of deictic gestures.

PURPOSE: In this study, the authors investigated the hypothesis that the perceived tight temporal synchrony of speech and gesture is evidence of an integrated spoken language and manual gesture communication system. It was hypothesized that experimental manipulations of the spoken response would affect the timing of deictic gestures. METHOD: The authors manipulated syllable position and contrastive stress in compound words in multiword utterances by using a repeated-measures design to investigate the degree of synchronization of speech and pointing gestures produced by 15 American English speakers. Acoustic measures were compared with the gesture movement recorded via capacitance. RESULTS: Although most participants began a gesture before the target word, the temporal parameters of the gesture changed as a function of syllable position and prosody. Syllables with contrastive stress in the 2nd position of compound words were the longest in duration and also most consistently affected the timing of gestures, as measured by several dependent measures. CONCLUSION: Increasing the stress of a syllable significantly affected the timing of a corresponding gesture, notably for syllables in the 2nd position of words that would not typically be stressed. The findings highlight the need to consider the interaction of gestures and spoken language production from a motor-based perspective of coordination.

Speech signal modification to increase intelligibility in noisy environments.

The role of transient speech components on speech intelligibility was investigated. Speech was decomposed into two components--quasi-steady-state (QSS) and transient--using a set of time-varying filters whose center frequencies and bandwidths were controlled to identify the strongest formant components in speech. The relative energy and intelligibility of the QSS and transient components were compared to original speech. Most of the speech energy was in the QSS component, but this component had low intelligibility. The transient component had much lower energy but was almost as intelligible as the original speech, suggesting that the transient component included speech elements important to speech perception. A modified version of speech was produced by amplifying the transient component and recombining it with the original speech. The intelligibility of the modified speech in background noise was compared to that of the original speech, using a psychoacoustic procedure based on the modified rhyme protocol. Word recognition rates for the modified speech were significantly higher at low signal-to-noise ratios (SNRs), with minimal effect on intelligibility at higher SNRs. These results suggest that amplification of transient information may improve the intelligibility of speech in noise and that this improvement is more effective in severe noise conditions.

The relationship among voice onset, voice quality, and fundamental frequency: a dynamical perspective.

In dynamical motor theory, skill acquisition occurs as a modification of preexisting coordination patterns or attractor states. The purpose of this study was to assess how different levels of voice onset, voice quality, and fundamental frequency (F(0)) combine to form the attractor states common to voice motor control. Three levels of voice onset (glottal, simultaneous, and breathy), voice quality (modal speech, mixed, and falsetto), and fundamental frequency (low, mid, and high) were manipulated by vocally untrained, female subjects. Percent correct of acquisition trials and self-report of effort were used as measures of stable phonations indicative of an attractor state. Using intensity as a covariate, the results provided support for two of the three predicted triads representing attractor states in female speakers: (1) glottal onset/modal speech quality/low F(0); and (2) breathy onset/falsetto quality/high F(0). The results of this study suggest that certain parameters of voice motor control, such as onset, quality, and F(0), exist as part of a dynamical system that can be identified and manipulated in voice motor acquisition and learning.

Lung volume effects on pharyngeal swallowing physiology.

The experiment was a prospective, repeated-measures design intended to determine how the variation of lung volume affects specific measures of swallowing physiology. Swallows were recorded in 28 healthy subjects, who ranged in age from 21 to 40 yr (mean age of 29 yr), by using simultaneous videofluoroscopy, bipolar intramuscular electromyography, and respiratory inductance plethysmography. Each subject swallowed three standardized pudding-like consistency boluses at three randomized lung volumes: total lung capacity, functional residual capacity, and residual volume. The results showed that pharyngeal activity duration of deglutition for swallows produced at residual volume was significantly longer than those occurring at total lung capacity or at functional residual capacity. No significant differences were found for bolus transit time or intramuscular electromyography of the superior constrictor. The results of this experiment lend support to the hypothesis that the respiratory system may have a regulatory function related to swallowing and that positive subglottic air pressure may be important for swallowing integrity. Eventually, new treatment paradigms for oropharyngeal dysphagia that are based on respiratory physiology may be developed.

Task-specific sensorimotor interactions in speech production.

Speaking involves the activity of multiple muscles moving many parts (articulators) of the vocal tract. In previous studies, it has been shown that mechanical perturbation delivered to one moving speech articulator, such as the lower lip or jaw, results in compensatory responses in the perturbed and other non-perturbed articulators, but not in articulators that are uninvolved in the specific speech sound being produced. These observations suggest that the speech motor control system may be organized in a task-specific manner. However, previous studies have not used the appropriate controls to address the mechanism by which this task-specific organization is achieved. A lack of response in a non-perturbed articulator may simply reflect the fact that the muscles examined were not active. Alternatively, there may be a specific gating of somatic sensory signals due to task requirements. The present study was designed to address the nature of the underlying sensorimotor organization. Unanticipated mechanical loads were applied to the upper lip during the "p" in "apa" and "f" in "afa" in six subjects. Both lips are used to produce "p", while only the lower lip is used for "f". For "apa", both upper lip and lower lip responses were observed following upper lip perturbation. For "afa", no upper lip or lower lip responses were observed following the upper lip perturbation. The differential response of the lower lip, which was phasically active during both speech tasks, indicates that the neural organization of these two speech tasks differs not only in terms of the different muscles used to produce the different movements, but also in terms of the sensorimotor interactions within and across the two lips.

Articulatory control of vowel length for contiguous jaw cycles: the effects of speaking rate and phonetic context.

The current study examined contiguous cycles of jaw movement in order to determine if select suprasegmental manipulations operate globally across the entire utterance, while phonetic changes are more locally administered. Specifically, articulatory kinematics were examined to determine if intra- and inter-articulatory spatial and temporal organization across manipulations of speaking rate was maintained for both jaw cycles while differing between the two cycles for phonetic changes (i.e., in coda composition) specific to the second jaw cycle. Five normal speakers repeated the syllables /paep/, /paeps/, and /paepst/, embedded in the carrier phrase, "Now say again," using slow, normal, and fast speaking rates. Measures were made of the magnitude of jaw opening peak velocity and time to peak velocity, as well as of coarticulatory overlap and interarticulator timing, for the first jaw cycle (jaw lowering for /eI/ in "say" to the first /p/) and the second jaw cycle (jaw lowering for /ae/ to the second /p/). The current data indicate that, for intra-articulatory kinematics, the manipulation of phonetic context resulted in localized adjustments, whereas the manipulation of speaking rate was applied globally across the utterance. Conversely, for inter-articulatory kinematics, the upper lip-jaw synergy was reconfigured across the utterance for manipulations of speaking rate, whereas this synergy was maintained for localized manipulations in phonetic context. Results are discussed with respect to motor strategies being flexibly implemented as a result of contextual variation and speech rate.