Rhythmic tapping difficulties in adults who stutter: A deficit in beat perception, motor execution, or sensorimotor integration?

OBJECTIVES: The study aims to better understand the rhythmic abilities of people who stutter and to identify which processes potentially are impaired in this population: (1) beat perception and reproduction; (2) the execution of movements, in particular their initiation; (3) sensorimotor integration. MATERIAL AND METHOD: Finger tapping behavior of 16 adults who stutter (PWS) was compared with that of 16 matching controls (PNS) in five rhythmic tasks of various complexity: three synchronization tasks - a simple 1:1 isochronous pattern, a complex non-isochronous pattern, and a 4 tap:1 beat isochronous pattern -, a reaction task to an aperiodic and unpredictable pattern, and a reproduction task of an isochronous pattern after passively listening. RESULTS: PWS were able to reproduce an isochronous pattern on their own, without external auditory stimuli, with similar accuracy as PNS, but with increased variability. This group difference in variability was observed immediately after passive listening, without prior motor engagement, and was not enhanced or reduced after several seconds of tapping. Although PWS showed increased tapping variability in the reproduction task as well as in synchronization tasks, this timing variability did not correlate significantly with the variability in reaction times or tapping force. Compared to PNS, PWS exhibited larger negative mean asynchronies, and increased synchronization variability in synchronization tasks. These group differences were not affected by beat hierarchy (i.e., "strong" vs. "weak" beats), pattern complexity (non-isochronous vs. isochronous) or presence versus absence of external auditory stimulus (1:1 vs. 1:4 isochronous pattern). Differences between PWS and PNS were not enhanced or reduced with sensorimotor learning, over the first taps of a synchronization task. CONCLUSION: Our observations support the hypothesis of a deficit in neuronal oscillators coupling in production, but not in perception, of rhythmic patterns, and a larger delay in multi-modal feedback processing for PWS.

Lip hyper-articulation in loud voice: Effect on resonance-harmonic proximity.

Men and women speakers were recorded while producing sustained vowels at comfortable and loud levels. Following comfortable speech, loud levels were produced in three different conditions: first without specific instruction (UL); then maintaining the same pitch as the comfortable level (PL); and finally, keeping both pitch and lip articulation constant (PAL). The sound pressure level, the fundamental frequency ( fo), the first two vocal tract resonances (R1 and R2), the lip geometry, and the larynx height were measured. For women, a closer proximity of R1 to its nearest harmonic, nfo, was observed in UL. However, no such increased proximity was found in PL, when speakers could, and did, hyper-articulate. Also, no increased proximity was observed in PAL, when lip articulation was constrained. No significant increase in R1: nfo proximity was observed in men in any of the three loud conditions. Finally, R2 was not observed significantly closer to a voice harmonic in loud speech, for neither men nor women.

The ConDialInt Model: Condensation, Dialogality, and Intentionality Dimensions of Inner Speech Within a Hierarchical Predictive Control Framework.

Inner speech has been shown to vary in form along several dimensions. Along condensation, condensed inner speech forms have been described, that are supposed to be deprived of acoustic, phonological and even syntactic qualities. Expanded forms, on the other extreme, display articulatory and auditory properties. Along dialogality, inner speech can be monologal, when we engage in internal soliloquy, or dialogal, when we recall past conversations or imagine future dialogs involving our own voice as well as that of others addressing us. Along intentionality, it can be intentional (when we deliberately rehearse material in short-term memory) or it can arise unintentionally (during mind wandering). We introduce the ConDialInt model, a neurocognitive predictive control model of inner speech that accounts for its varieties along these three dimensions. ConDialInt spells out the condensation dimension by including inhibitory control at the conceptualization, formulation or articulatory planning stage. It accounts for dialogality, by assuming internal model adaptations and by speculating on neural processes underlying perspective switching. It explains the differences between intentional and spontaneous varieties in terms of monitoring. We present an fMRI study in which we probed varieties of inner speech along dialogality and intentionality, to examine the validity of the neuroanatomical correlates posited in ConDialInt. Condensation was also informally tackled. Our data support the hypothesis that expanded inner speech recruits speech production processes down to articulatory planning, resulting in a predicted signal, the inner voice, with auditory qualities. Along dialogality, covertly using an avatar's voice resulted in the activation of right hemisphere homologs of the regions involved in internal own-voice soliloquy and in reduced cerebellar activation, consistent with internal model adaptation. Switching from first-person to third-person perspective resulted in activations in precuneus and parietal lobules. Along intentionality, compared with intentional inner speech, mind wandering with inner speech episodes was associated with greater bilateral inferior frontal activation and decreased activation in left temporal regions. This is consistent with the reported subjective evanescence and presumably reflects condensation processes. Our results provide neuroanatomical evidence compatible with predictive control and in favor of the assumptions made in the ConDialInt model.

Hyper-articulation in Lombard speech: An active communicative strategy to enhance visible speech cues?

This study investigates the hypothesis that speakers make active use of the visual modality in production to improve their speech intelligibility in noisy conditions. Six native speakers of Canadian French produced speech in quiet conditions and in 85 dB of babble noise, in three situations: interacting face-to-face with the experimenter (AV), using the auditory modality only (AO), or reading aloud (NI, no interaction). The audio signal was recorded with the three-dimensional movements of their lips and tongue, using electromagnetic articulography. All the speakers reacted similarly to the presence vs absence of communicative interaction, showing significant speech modifications with noise exposure in both interactive and non-interactive conditions, not only for parameters directly related to voice intensity or for lip movements (very visible) but also for tongue movements (less visible); greater adaptation was observed in interactive conditions, though. However, speakers reacted differently to the availability or unavailability of visual information: only four speakers enhanced their visible articulatory movements more in the AV condition. These results support the idea that the Lombard effect is at least partly a listener-oriented adaptation. However, to clarify their speech in noisy conditions, only some speakers appear to make active use of the visual modality.

Vocal Change Patterns During a Teaching Day: Inter- and Intra-subject Variability.

OBJECTIVES: To describe the mean voice changes of 22 female teachers during a typical workday, examine the inter- and intra-subject variability, and establish a typology of different voice patterns during the workday. METHODS: For each participant, fundamental frequency (F0), harmonics-to-noise ratio (HNR), jitter, and shimmer were measured on sustained vowels at the beginning and at the end of the workday, at three different times during the school year. RESULTS: The group mean pattern showed significant increases in F0 and HNR during the workday and significant decreases in jitter and shimmer. However, considerable inter- and intra-subject variability was observed. Based on the variation in the acoustic parameters during the workday, three different voice patterns were identified. The first is characterized by a greater F0 increase during the day, interpreted as a common, appropriate adaptation to vocal load. The second is characterized by a greater increase in HNR during the day and greater decreases in jitter and shimmer, interpreted as hyperfunctional voice production. The third is characterized by greater decreases in F0 and HNR and greater increases in jitter and shimmer, suggesting acute inflammation or muscle fatigue following the workday. CONCLUSIONS: The observed variety of vocal patterns during the workday emphasizes the need to study this phenomenon individually and target different types of behaviors to develop tailored prevention and treatment methods.

Physiological and acoustic characteristics of the male music theatre voice.

Six male music theatre singers were recorded in three different voice qualities: legit and two types of belt ("chesty" and "twangy"), on two vowels ([e] and [ɔ]), at four increasing pitches in the upper limit of each singer's belt range (∼250-440 Hz). The audio signal, the electroglottographic (EGG) signal, and the vocal tract impedance were all measured simultaneously. Voice samples were analyzed and then evaluated perceptually by 16 expert listeners. The three qualities were produced with significant differences at the physiological, acoustical, and perceptual levels: Singers produced belt qualities with a higher EGG contact quotient (CQEGG) and greater contacting speed quotient (Qcs), greater sound pressure level (SPL), and energy above 1 kHz (alpha ratio), and with higher frequencies of the first two vocal tract resonances (fR1, fR2), especially in the upper pitch range when compared to legit. Singers produced the chesty belt quality with higher CQEGG, Qcs, and SPL values and lower alpha ratios over the whole belt range, and with higher fR1 at the higher pitch range when compared to twangy belt. Consistent tuning of fR1 to the second voice harmonic (2f0) was observed in all three qualities and for both vowels. Expert listeners tended to identify all qualities based on the same acoustical and physiological variations as those observed in the singers' intended qualities.

Neural correlates of phonetic convergence and speech imitation.

Speakers unconsciously tend to mimic their interlocutor's speech during communicative interaction. This study aims at examining the neural correlates of phonetic convergence and deliberate imitation, in order to explore whether imitation of phonetic features, deliberate, or unconscious, might reflect a sensory-motor recalibration process. Sixteen participants listened to vowels with pitch varying around the average pitch of their own voice, and then produced the identified vowels, while their speech was recorded and their brain activity was imaged using fMRI. Three degrees and types of imitation were compared (unconscious, deliberate, and inhibited) using a go-nogo paradigm, which enabled the comparison of brain activations during the whole imitation process, its active perception step, and its production. Speakers followed the pitch of voices they were exposed to, even unconsciously, without being instructed to do so. After being informed about this phenomenon, 14 participants were able to inhibit it, at least partially. The results of whole brain and ROI analyses support the fact that both deliberate and unconscious imitations are based on similar neural mechanisms and networks, involving regions of the dorsal stream, during both perception and production steps of the imitation process. While no significant difference in brain activation was found between unconscious and deliberate imitations, the degree of imitation, however, appears to be determined by processes occurring during the perception step. Four regions of the dorsal stream: bilateral auditory cortex, bilateral supramarginal gyrus (SMG), and left Wernicke's area, indeed showed an activity that correlated significantly with the degree of imitation during the perception step.

Converging toward a common speech code: imitative and perceptuo-motor recalibration processes in speech production.

Auditory and somatosensory systems play a key role in speech motor control. In the act of speaking, segmental speech movements are programmed to reach phonemic sensory goals, which in turn are used to estimate actual sensory feedback in order to further control production. The adult's tendency to automatically imitate a number of acoustic-phonetic characteristics in another speaker's speech however suggests that speech production not only relies on the intended phonemic sensory goals and actual sensory feedback but also on the processing of external speech inputs. These online adaptive changes in speech production, or phonetic convergence effects, are thought to facilitate conversational exchange by contributing to setting a common perceptuo-motor ground between the speaker and the listener. In line with previous studies on phonetic convergence, we here demonstrate, in a non-interactive situation of communication, online unintentional and voluntary imitative changes in relevant acoustic features of acoustic vowel targets (fundamental and first formant frequencies) during speech production and imitation. In addition, perceptuo-motor recalibration processes, or after-effects, occurred not only after vowel production and imitation but also after auditory categorization of the acoustic vowel targets. Altogether, these findings demonstrate adaptive plasticity of phonemic sensory-motor goals and suggest that, apart from sensory-motor knowledge, speech production continuously draws on perceptual learning from the external speech environment.

Physiological and acoustic characteristics of the female Music Theater voice.

Three Music Theater vocal qualities ("chesty belt," "twangy belt," and "legit") were investigated in female singers at their overlap range, between F#4-D5 (~370-600 Hz). Six experienced Music Theater singers performed each quality on two different vowels ([e], [ɔ]). Audio and electroglottographic (EGG) signals were recorded as well as the vocal tract impedance. In chesty belt and twangy belt, singers systematically tuned the frequency of their first vocal tract resonance (R1) to the second harmonic (2f(0)) up to C5. R1 remained lower in frequency for the legit quality. No tuning of the second vocal tract resonance (R2) was observed in any of these qualities although R2 frequency was significantly higher in both belt qualities than in legit. Closed quotient, degree of symmetry of the EGG waveform, sound pressure level (SPL) and the energy of the spectrum above 1 kHz were significantly greater in chesty belt than in legit but not significantly different between chesty belt and twangy belt qualities. A fourth quality ("mix") was explored in three singers. Different production strategies were observed for each singer, with values of spectral, glottal and vocal tract descriptors found in between those measured for legit and chesty belt qualities.

Glottal behavior in the high soprano range and the transition to the whistle register.

The high soprano range was investigated by acoustic and electroglottographic measurements of 12 sopranos and high-speed endoscopy of one of these. A single laryngeal transition was observed on glissandi above the primo passaggio. It supports the existence of two distinct laryngeal mechanisms in the high soprano range: M2 and M3, underlying head and whistle registers. The laryngeal transition occurred gradually over several tones within the interval D#5-D6. It occurred over a wider range and was completed at a higher pitch for trained than untrained sopranos. The upper limit of the laryngeal transition during glissandi was accompanied by pitch jumps or instabilities, but, for most singers, it did not coincide with the upper limit of R1:f(0) tuning (i.e., tuning the first resonance to the fundamental frequency). However, pitch jumps could also be associated with changes in resonance tuning. Four singers demonstrated an overlap range over which they could sing with a full head or fluty resonant quality. Glottal behaviors underlying these two qualities were similar to the M2 and M3 mechanisms respectively. Pitch jumps and discontinuous glottal and spectral changes characteristic of a M2-M3 laryngeal transition were observed on decrescendi produced within this overlap range.

Vocal tract adjustments in the high soprano range.

Twelve sopranos with different levels of expertise (4 nonexperts, 4 advanced, 4 professionals) sustained pitches from A4 ( approximately 440 Hz) to their highest pitch (ranging from C6 to D7, i.e., from approximately 1000 to 2300 Hz). The frequencies of their first two vocal tract resonances (R1 and R2) were measured by broadband excitation at the mouth and compared with the voice harmonics (f(0), 2f(0), etc). Lip articulation was measured from simultaneous video recordings. Adjustment of R1 near to f(0) (R1:f(0) tuning) was observed below C6 to D6 ( approximately 1000-1200 Hz) for both expert and non-expert singers. Experts began this tuning at lower pitches. Some singers combine R2:2f(0) adjustment with R1:f(0) tuning. Some singers increased mouth area with increasing pitch over the whole R1:f(0) tuning range. Other singers showed this strategy on the higher part of the R1:f(0) range only, and used another, as yet unidentified, articulatory strategy on the lower part. To achieve very high pitches, some singers extended the range of R1:f(0) tuning as far as E6 to F#6 ( approximately 1300-1500 Hz) while others adjusted R2 near f(0) over the highest pitch range.

Influence of sound immersion and communicative interaction on the Lombard effect.

PURPOSE: To examine the influence of sound immersion techniques and speech production tasks on speech adaptation in noise. METHOD: In Experiment 1, we compared the modification of speakers' perception and speech production in noise when noise is played into headphones (with and without additional self-monitoring feedback) or over loudspeakers. We also examined how this sound immersion effect depends on noise type (broadband or cocktail party) and level (from 62 to 86dB SPL). In Experiment 2, we compared the modification of acoustic and lip articulatory parameters in noise when speakers interact or not with a speech partner. RESULTS: Speech modifications in noise were greater when cocktail party noise was played in headphones than over loudspeakers. Such an effect was less noticeable in broadband noise. Adding a self-monitoring feedback into headphones reduced this effect but did not completely compensate for it. Speech modifications in noise were greater in interactive situation and concerned parameters that may not be related to voice intensity. CONCLUSIONS: The results support the idea that the Lombard effect is both a communicative adaptation and an automatic regulation of vocal intensity. The influence of auditory and communicative factors has some methodological implications on the choice of appropriate paradigms to study the Lombard effect.

Vocal tract resonances in speech, singing, and playing musical instruments.

IN BOTH THE VOICE AND MUSICAL WIND INSTRUMENTS, A VALVE (VOCAL FOLDS, LIPS, OR REED) LIES BETWEEN AN UPSTREAM AND DOWNSTREAM DUCT: trachea and vocal tract for the voice; vocal tract and bore for the instrument. Examining the structural similarities and functional differences gives insight into their operation and the duct-valve interactions. In speech and singing, vocal tract resonances usually determine the spectral envelope and usually have a smaller influence on the operating frequency. The resonances are important not only for the phonemic information they produce, but also because of their contribution to voice timbre, loudness, and efficiency. The role of the tract resonances is usually different in brass and some woodwind instruments, where they modify and to some extent compete or collaborate with resonances of the instrument to control the vibration of a reed or the player's lips, andor the spectrum of air flow into the instrument. We give a brief overview of oscillator mechanisms and vocal tract acoustics. We discuss recent and current research on how the acoustical resonances of the vocal tract are involved in singing and the playing of musical wind instruments. Finally, we compare techniques used in determining tract resonances and suggest some future developments.