Influence of consonant voicing characteristics on sentence production in abductor versus adductor spasmodic dysphonia.

OBJECTIVES/HYPOTHESIS: This study evaluated the hypotheses that sentence production by speakers with adductor (AD) and abductor (AB) spasmodic dysphonia (SD) may be differentially influenced by consonant voicing and manner features, in comparison with healthy, matched, nondysphonic controls. STUDY DESIGN: This was a prospective, single blind study, using a between-groups, repeated measures design for the independent variables of perceived voice quality and sentence duration. METHODS: Sixteen subjects with ADSD and 10 subjects with ABSD, as well as 26 matched healthy controls produced four short, simple sentences that were systematically loaded with voiced or voiceless consonants of either obstruant or continuant manner categories. Experienced voice clinicians, who were "blind" as to speakers' group affixations, used visual analog scaling to judge the overall voice quality of each sentence. Acoustic sentence durations were also measured. RESULTS: Speakers with ABSD or ADSD demonstrated significantly poorer than normal voice quality on all sentences. Speakers with ABSD exhibited longer than normal duration for voiceless consonant sentences. Speakers with ADSD had poorer voice quality for voiced than for voiceless consonant sentences. Speakers with ABSD had longer durations for voiceless than for voiced consonant sentences. CONCLUSIONS: The two subtypes of SD exhibit differential performance on the basis of consonant voicing in short, simple sentences; however, each subgroup manifested voicing-related differences on a different variable (voice quality vs sentence duration). Findings suggest different underlying pathophysiological mechanisms for ABSD and ADSD. Findings also support inclusion of short, simple sentences containing voiced or voiceless consonants as part of the diagnostic protocol for SD, with measurement of sentence duration in addition to judments of voice quality severity.

Functional flexibility of infant vocalization and the emergence of language.

We report on the emergence of functional flexibility in vocalizations of human infants. This vastly underappreciated capability becomes apparent when prelinguistic vocalizations express a full range of emotional content--positive, neutral, and negative. The data show that at least three types of infant vocalizations (squeals, vowel-like sounds, and growls) occur with this full range of expression by 3-4 mo of age. In contrast, infant cry and laughter, which are species-specific signals apparently homologous to vocal calls in other primates, show functional stability, with cry overwhelmingly expressing negative and laughter positive emotional states. Functional flexibility is a sine qua non in spoken language, because all words or sentences can be produced as expressions of varying emotional states and because learning conventional "meanings" requires the ability to produce sounds that are free of any predetermined function. Functional flexibility is a defining characteristic of language, and empirically it appears before syntax, word learning, and even earlier-developing features presumed to be critical to language (e.g., joint attention, syllable imitation, and canonical babbling). The appearance of functional flexibility early in the first year of human life is a critical step in the development of vocal language and may have been a critical step in the evolution of human language, preceding protosyntax and even primitive single words. Such flexible affect expression of vocalizations has not yet been reported for any nonhuman primate but if found to occur would suggest deep roots for functional flexibility of vocalization in our primate heritage.

Identification of prelinguistic phonological categories.

PURPOSE: The prelinguistic infant's babbling repertoire of syllables--the phonological categories that form the basis for early word learning--is noticed by caregivers who interact with infants around them. Prior research on babbling has not explored the caregiver's role in recognition of early vocal categories as foundations for word learning. In the present work, the authors begin to address this gap. METHOD: The authors explored vocalizations produced by 8 infants at 3 ages (8, 10, and 12 months) in studies illustrating identification of phonological categories through caregiver report, laboratory procedures simulating the caregiver's natural mode of listening, and the more traditional laboratory approach (phonetic transcription). RESULTS: Caregivers reported small repertoires of syllables for their infants. Repertoires of similar size and phonetic content were discerned in the laboratory by judges who simulated the caregiver's natural mode of listening. However, phonetic transcription with repeated listening to infant recordings yielded repertoire sizes that vastly exceeded those reported by caregivers and naturalistic listeners. CONCLUSIONS: The results suggest that caregiver report and naturalistic listening by laboratory staff can provide a new way to explore key characteristics of early infant vocal categories, a way that may provide insight into later speech and language development.

Sentence intelligibility before and after voice treatment in speakers with idiopathic Parkinson's disease.

OBJECTIVES/HYPOTHESIS: The purpose of this study was to determine whether sentence intelligibility improves in speakers with idiopathic Parkinson's disease (PD) as a result of Lee Silverman Voice Treatment (LSVT). It was hypothesized that all the speakers would improve following treatment, in association with increased vocal loudness, which was the primary target of the treatment. STUDY DESIGN: Prospective study of eight Speakers with PD using a single-blinded, randomized pre-post treatment design, with multiple daily assessments before and after treatment was carried out. Resultant data were corrected for regression to the mean. METHODS: Randomized digital recordings of sentences produced by speakers with idiopathic PD before and after the treatment were presented to normal-hearing listeners with equalized intensity at conversational loudness in the presence of pink noise. Percentage of words understood was calculated before and after the treatment. Changes in overall vocal intensity were also analyzed. RESULTS: There was a statistically significant group effect from pre-to-post voice treatment; however, there was also significant interaction of treatment with speakers. Six of the speakers with PD improved significantly following voice treatment, one exhibited no change, and one exhibited a decline in sentence intelligibility post-treatment. CONCLUSIONS: LSVT yielded significant improvement in sentence intelligibility for most speakers in the study but was not beneficial for two of the speakers despite the fact that they increased their overall vocal loudness.

Vocal aging and adductor spasmodic dysphonia: response to botulinum toxin injection.

Aging of the larynx is characterized by involutional changes which alter its biomechanical and neural properties and create a biological environment that is different from younger counterparts. Illustrative anatomical examples are presented. This natural, non-disease process appears to set conditions which may influence the effectiveness of botulinum toxin injection and our expectations for its success. Adductor spasmodic dysphonia, a type of laryngeal dystonia, is typically treated using botulinum toxin injections of the vocal folds in order to suppress adductory muscle spasms which are disruptive to production of speech and voice. A few studies have suggested diminished response to treatment in older patients with adductor spasmodic dysphonia. This retrospective study provides a reanalysis of existing pre-to-post treatment data as function of age. Perceptual judgments of speech produced by 42 patients with ADSD were made by two panels of professional listeners with expertise in voice or fluency of speech. Results demonstrate a markedly reduced positive response to botulinum toxin treatment in the older patients. Perceptual findings are further elucidated by means of acoustic spectrography. Literature on vocal aging is reviewed to provide a specific set of biological mechanisms that best account for the observed interaction of botulinum toxin treatment with advancing age.

Vibratory regime classification of infant phonation.

Infant phonation is highly variable in many respects, including the basic vibratory patterns by which the vocal tissues create acoustic signals. Previous studies have identified the regular occurrence of nonmodal phonation types in normal infant phonation. The glottis is like many oscillating systems that, because of nonlinear relationships among the elements, may vibrate in ways representing the deterministic patterns classified theoretically within the mathematical framework of nonlinear dynamics. The infant's preverbal vocal explorations present such a variety of phonations that it may be possible to find effectively all the classes of vibration predicted by nonlinear dynamic theory. The current report defines acoustic criteria for an important subset of such vibratory regimes, and demonstrates that analysts can be trained to reliably use these criteria for a classification that includes all instances of infant phonation in the recorded corpora. The method is thus internally comprehensive in the sense that all phonations are classified, but it is not exhaustive in the sense that all vocal qualities are thereby represented. Using the methods thus developed, this study also demonstrates that the distributions of these phonation types vary significantly across sessions of recording in the first year of life, suggesting developmental changes. The method of regime classification is thus capable of tracking changes that may be indicative of maturation of the mechanism, the learning of categories of phonatory control, and the possibly varying use of vocalizations across social contexts.

Spectral amplitude measures of adductor spasmodic dysphonic speech.

Spectral amplitude measures are sensitive to varying degrees of vocal fold adduction in normal speakers. This study examined the applicability of harmonic amplitude differences to adductor spasmodic dysphonia (ADSD) in comparison with normal controls. Amplitudes of the first and second harmonics (H1, H2) and of harmonics affiliated with the first, second, and third formants (A1, A2, A3) were obtained from spectra of vowels and /i/ excerpted from connected speech. Results indicated that these measures could be made reliably in ADSD. With the exception of H1(*)-H2(*), harmonic amplitude differences (H1(*)-A1, H1(*)-A2, and H1(*)-A3(*)) exhibited significant negative linear relationships (P < 0.05) with clinical judgments of overall severity. The four harmonic amplitude differences significantly differentiated between pre-BT and post-BT productions (P < 0.05). After treatment, measurements from detected significant differences between ADSD and normal controls (P < 0.05), but measurements from /i/ did not. LTAS analysis of ADSD patients' speech samples proved a good fit with harmonic amplitude difference measures. Harmonic amplitude differences also significantly correlated with perceptual judgments of breathiness and roughness (P < 0.05). These findings demonstrate high clinical applicability for harmonic amplitude differences for characterizing phonation in the speech of persons with ADSD, as well as normal speakers, and they suggest promise for future application to other voice pathologies.