Browsing by Subject "Voice disorders"

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    Muscle tension dysphonia as a disorder of motor learning
    (2013-04) Urberg-Carlson, Kari Elizabeth
    Background: Adaptive learning has been demonstrated in many areas of motor learning. In speech, adaptive responses to auditory perturbation of fundamental frequency, formant frequencies and centroid frequencies of fricatives have been demonstrated. This dissertation presents the hypothesis that the motor changes observed in muscle tension dysphonia may be due to adaptive learning. To begin to test this hypothesis, an experiment was designed to look for evidence of an adaptive learning response to imposed auditory perturbation of voice quality. Methods: 16 participants repeated the syllable /ha/ while listening to noise under a number of experimental conditions. The training condition presented a re-synthesized recording of the participants own voices, which had an artificially increased noise-toharmonic ratio intended to simulate breathiness. A control condition presented speech babble at the same intensity. Catch trials in which the noise was turned off were included to test for evidence of motor learning, and trials where the participants repeated /he/ were included to test for evidence of generalization to untrained stimuli. H1-H2, a measure of spectral slant, was the dependent measure. A second experiment compared participants’ performance on a task of auditory perception of breathiness to their response to the auditory perturbation. Results: 12 of 16 participants showed statistically different values of H1-H2 between the training and control conditions. As none of the group differences between conditions were significant, this experiment was not able to demonstrate adaptive learning. There was no relationship between performance on the auditory perception task and performance on the adaptive learning task. Conclusions: Given the large body of evidence supporting the concept of adaptive learning in many domains of motor behavior, it is unlikely that behaviors that control voice quality are not subject to adaptive learning. Limitations of the experiment are discussed.
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    Pathophysiology of adductor spasmodic dysphonia: a TMS study
    (2012-09) Samargia, Sharyl Anne
    Adductor spasmodic dysphonia (AdSD) is a neurologically-based voice disorder affecting the firing rate and pattern of upper motor neurons responsible for the laryngeal musculature. AdSD is characterized by intermittent hyperadduction of the true vocal folds during connected speech resulting in interruptions in phonation and a strained/struggled vocal quality. Differential diagnosis of AdSD can be difficult as the clinical symptoms present similar to those found in muscle tension dysphonia (MTD). Purpose: The purpose of this study was to identify and compare differences in intracortical inhibition and facilitation in the primary motor cortex between those with AdSD, MTD and healthy controls, if those differences were widespread; affecting both the cortical spinal and corticobulbar tract and, if differences in cortical excitability are related to the perceptual severity of the voice disorder. An additional purpose was to determine if measures of intracortical inhibition and facilitation are viable methods to assist in the differential diagnosis between AdSD and MTD. Methods: Transcranial magnetic stimulation (TMS) was used to measure intracortical inhibition and facilitation through the following measures: cortical silent period (CSP), short interval intracortical inhibition (SICI), intracortical facilitation (ICF) and the stimulus response curve (SR curve) in first dorsal interosseus and masseter in those with AdSD, MTD and healthy controls. The Consensus of Auditory Perceptual Evaluation of Voice (CAPE-V) was used as a tool to evaluate the nature and severity of voice characteristics of those with AdSD and MTD. Results: Masseter and FDI CSP were the most sensitive in capturing between group differences. Those with AdSD had significantly shorter CSP duration in masseter than those with MTD and healthy controls. Those with AdSD also had significantly shorter CSP duration in FDI than healthy controls, but not those with MTD indicating widespread dysfunction of the GABAB mechanism is a feature of AdSD, similar to other forms of focal dystonia. Use of TMS is feasible in assisting in the differential diagnosis of AdSD and MTD.