Acoustic and Aerodynamic Comparisons of Voice Qualities Produced After Voice Training.

Characteristics of true vocal fold vibration such as the proportion of closed phase of vibration to open phase, longitudinal tension, and the amount of medial compression are used to define four conditions during Estill Voice Training. However, it is unknown whether trainees achieve these phonatory differences after training. Acoustic and aerodynamic measures were used to determine differences in Slack, Thick, Thin, and Stiff conditions. Twenty-four female speech-language pathology graduate students received training perceiving and producing these four conditions and volunteered to participate 3-5 months later. After a 20-minute refresher training, participants were recorded using the Phonatory Aerodynamic System with electroglottography and Computerized Speech Lab. Four Estill Voice Training experts independently categorized the voice quality productions. Aerodynamic and acoustic measures of productions classified by at least three of four experts as having the intended quality determined if measures differentiated among voice qualities and supported the hypothesized physiological concepts used in training at Bonferroni corrected P ≤ 0.0063. Results showed that Slack had low fundamental frequency (fo), low sound pressure level (SPL), and high vibratory instability; Thick had high subglottal pressure (Psg), high SPL, and high vibratory stability; Stiff had high airflow while Thin had lower Psg than Thick. Seven measures differentiated the four qualities with 88.1% accuracy while only Psg, airflow, and jitter were required to differentiate Thick, Stiff, and Thin with 88.7% accuracy. As acoustic and aerodynamic measures differentiated among voice qualities and supported the theoretical physiological characteristics used in training, they could be used to track accuracy during training.

Functional near-infrared spectroscopy for speech protocols: characterization of motion artifacts and guidelines for improving data analysis.

Monitoring speech tasks with functional near-infrared spectroscopy (fNIRS) enables investigation of speech production mechanisms and informs treatment strategies for speech-related disorders such as stuttering. Unfortunately, due to movement of the temporalis muscle, speech production can induce relative movement between probe optodes and skin. These movements generate motion artifacts during speech tasks. In practice, spurious hemodynamic responses in functional activation signals arise from lack of information about the consequences of speech-related motion artifacts, as well as from lack of standardized processing procedures for fNIRS signals during speech tasks. To this end, we characterize the effects of speech production on fNIRS signals, and we introduce a systematic analysis to ameliorate motion artifacts. The study measured 50 healthy subjects performing jaw movement (JM) tasks and found that JM produces two different patterns of motion artifacts in fNIRS. To remove these unwanted contributions, we validate a hybrid motion-correction algorithm based sequentially on spline interpolation and then wavelet filtering. We compared performance of the hybrid algorithm with standard algorithms based on spline interpolation only and wavelet decomposition only. The hybrid algorithm corrected 94% of the artifacts produced by JM, and it did not lead to spurious responses in the data. We also validated the hybrid algorithm during a reading task performed under two different conditions: reading aloud and reading silently. For both conditions, we observed significant cortical activation in brain regions related to reading. Moreover, when comparing the two conditions, good agreement of spatial and temporal activation patterns was found only when data were analyzed using the hybrid approach. Overall, the study demonstrates a standardized processing scheme for fNIRS data during speech protocols. The scheme decreases spurious responses and intersubject variability due to motion artifacts.

In vivo oxygen consumption and hemoglobin levels in human thyroarytenoid muscle.

OBJECTIVES/HYPOTHESIS: Visible light spectroscopy (VLS) is the technology behind the Food and Drug Administration-approved TSTAT device that is used to monitor tissue oxygen (StO(2)) and relative total hemoglobin (rtHb) levels by measuring reflected visible light. The purpose of this novel, pilot study was to determine if VLS is a reliable and valid method of measuring StO(2) and rtHb levels in the human thyroarytenoid/lateral cricoarytenoid (TA-LCA) muscle complex, thus providing information about vocal fold muscle physiology. STUDY DESIGN: Pre-test/post-test with mulitple baselines and two conditions. METHODS: VLS measurements were taken at baseline, during exercise, and following recovery on six subjects using both noncontact channel-port endoscope (endo-probe) and laryngeal electromyography (LEMG) needle-guided techniques. RESULTS: The average baseline StO(2) was 69% (standard deviation [SD] = 3.6%) for the LEMG-guided probe and was 71.5% (SD = 2.8%) for the endo-probe. During phonation, the StO(2) for the LEMG-guided probe dropped to 59% (SD = 7%; P = .04). Mean rtHb measured by the LEMG probe rose from a baseline of 144 µM (SD = 165 µM) to 214 µM (SD = 166 µM, P = .34) during phonation and back to 149 µM (SD = 139 µM, P = .85) after recovery. Mean rtHb as measured using the endo-probe at baseline and after recovery was 104 µM (SD = 30 µM, P = .76). CONCLUSIONS: VLS can be used to measure changes in StO(2) and rtHb levels pre- and postexercise in the human TA-LCA muscle complex.

Cytochrome c oxidase deficiency in human posterior cricoarytenoid muscle.

BACKGROUND: Mitochondrial alterations occur in skeletal muscle fibers throughout the normal aging process, resulting from increased accumulation of reactive oxide species (ROS). These result in respiratory chain abnormalities, which decrease the oxidative capacity of muscle fibers, leading to decreased contractile force, sarcopenia, or fiber necrosis. Intrinsic laryngeal muscles are a cranial muscle group that possesses some distinctive genotypic, phenotypic, and physiologic properties. Their susceptibility to mitochondrial alterations resulting from biological processes that increase levels of oxidative stress may be one of these distinctive characteristics. OBJECTIVES: The incidence of cytochrome c oxidase (COX) deficiency (COX(-)) was determined in human posterior cricoarytenoid (PCA) muscle when compared with the human thyrohyoid (TH) muscle, an extrinsic laryngeal muscle that served as "control" muscle. Ten PCA and 10 TH muscles were harvested postlaryngectomy from 10 subjects ranging in age from 55 to 86 years. Differences in COX(-) were compared within and between muscle types using tissue section staining and standard morphometric analysis. RESULTS AND CONCLUSIONS: COX(-) fibers were identified in both the PCA and TH muscles. The PCA muscle had 10 times as may affected fibers as the TH muscle, with significant differences in COX(-) found between muscle type and fiber type (P=0.003). Almost all of this effect was the result of elevated levels of COX(-) in type I fibers from the PCA muscle (P=0.002) that showed a strong positive correlation with increased age. These results suggest that increased mitochondrial alterations may occur in the PCA muscle during normal aging.

Anatomy and fiber type composition of human interarytenoid muscle.

Intrinsic laryngeal muscle investigations, especially those of the interarytenoid (IA) muscle, have been primarily teleologically based. We determined IA muscle anatomy and histochemical and immunohistochemical classification of extrafusal and intrafusal (muscle spindle) fibers in 5 patients. Extrafusal fibers were oxidative type I and glycolytic types IIA and IIX. Intrafusal fibers of muscle spindles were identified by the presence of tonic and neonatal myosin. The results demonstrate that the IA muscle has a phenotype similar to that of limb skeletal muscle. Myosin coexpression, the absence of intrafusal fibers, and fiber type grouping were unusual features found previously in the thyroarytenoid and posterior cricoarytenoid muscles, but they were not present in the IA muscle. These findings lead to the conclusion that the IA muscle has functional significance beyond its assumed importance in maintaining vocal fold position during phonation. The presence of spindles demonstrates differences in motor control as compared to the thyroarytenoid and posterior cricoarytenoid muscles. Further, extrafusal fiber characteristics implicate IA muscle involvement in muscle tension dysphonia and adductor spasmodic dysphonia. Given the unique physiologic characteristics of the human IA muscle, further research into the role of the IA muscle in voice disorders is warranted.