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Previous studies have found that the detection of near-threshold stimuli is decreased immediately before movement and throughout movement production. This has been suggested to occur through the use of the internal forward model processing an efferent copy of the motor command and creating a prediction that is used to cancel

Previous studies have found that the detection of near-threshold stimuli is decreased immediately before movement and throughout movement production. This has been suggested to occur through the use of the internal forward model processing an efferent copy of the motor command and creating a prediction that is used to cancel out the resulting sensory feedback. Currently, there are no published accounts of the perception of tactile signals for motor tasks and contexts related to the lips during both speech planning and production. In this study, we measured the responsiveness of the somatosensory system during speech planning using light electrical stimulation below the lower lip by comparing perception during mixed speaking and silent reading conditions. Participants were asked to judge whether a constant near-threshold electrical stimulation (subject-specific intensity, 85% detected at rest) was present during different time points relative to an initial visual cue. In the speaking condition, participants overtly produced target words shown on a computer monitor. In the reading condition, participants read the same target words silently to themselves without any movement or sound. We found that detection of the stimulus was attenuated during speaking conditions while remaining at a constant level close to the perceptual threshold throughout the silent reading condition. Perceptual modulation was most intense during speech production and showed some attenuation just prior to speech production during the planning period of speech. This demonstrates that there is a significant decrease in the responsiveness of the somatosensory system during speech production as well as milliseconds before speech is even produced which has implications for speech disorders such as stuttering and schizophrenia with pronounced deficits in the somatosensory system.
ContributorsMcguffin, Brianna Jean (Author) / Daliri, Ayoub (Thesis director) / Liss, Julie (Committee member) / Department of Psychology (Contributor) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05
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Description
Children with cleft palate with or without cleft lip (CP+/-L) often demonstrate disordered speech. Clinicians and researchers have a goal for children with CP+/-L to demonstrate typical speech when entering kindergarten; however, this benchmark is not routinely met. There is a large body of previous research examining speech articulation skills

Children with cleft palate with or without cleft lip (CP+/-L) often demonstrate disordered speech. Clinicians and researchers have a goal for children with CP+/-L to demonstrate typical speech when entering kindergarten; however, this benchmark is not routinely met. There is a large body of previous research examining speech articulation skills in this clinical population; however, there are continued questions regarding the severity of articulation deficits in children with CP+/-L, especially for the age range of children entering school. This dissertation aimed to provide additional information on speech accuracy and speech error usage in children with CP+/-L between the ages of four and seven years. Additionally, it explored individual and treatment characteristics that may influence articulation skills. Finally, it examined the relationship between speech accuracy during a sentence repetition task versus during a single-word naming task.

Children with CP+/-L presented with speech accuracy that differed according to manner of production. Speech accuracy for fricative phonemes was influenced by severity of hypernasality, although age and status of secondary surgery did not influence speech accuracy for fricatives. For place of articulation, children with CP+/-L demonstrated strongest accuracy of production for bilabial and velar phonemes, while alveolar and palatal phonemes were produced with lower accuracy. Children with clefting that involved the lip and alveolus demonstrated reduced speech accuracy for alveolar phonemes compared to children with clefts involving the hard and soft palate only.

Participants used a variety of speech error types, with developmental/phonological errors, anterior oral cleft speech characteristics, and compensatory errors occurring most frequently across the sample. Several factors impacted the type of speech errors used, including cleft type, severity of hypernasality, and age.

The results from this dissertation project support previous research findings and provide additional information regarding the severity of speech articulation deficits according to manner and place of consonant production and according to different speech error categories. This study adds information on individual and treatment characteristics that influenced speech accuracy and speech error usage.
ContributorsLien, Kari (Author) / Scherer, Nancy J. (Thesis advisor) / Nett Cordero, Kelly (Committee member) / Liss, Julie (Committee member) / Sitzman, Thomas (Committee member) / Arizona State University (Publisher)
Created2020
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Description
Speech intelligibility measures how much a speaker can be understood by a listener. Traditional measures of intelligibility, such as word accuracy, are not sufficient to reveal the reasons of intelligibility degradation. This dissertation investigates the underlying sources of intelligibility degradations from both perspectives of the speaker and the listener. Segmental

Speech intelligibility measures how much a speaker can be understood by a listener. Traditional measures of intelligibility, such as word accuracy, are not sufficient to reveal the reasons of intelligibility degradation. This dissertation investigates the underlying sources of intelligibility degradations from both perspectives of the speaker and the listener. Segmental phoneme errors and suprasegmental lexical boundary errors are developed to reveal the perceptual strategies of the listener. A comprehensive set of automated acoustic measures are developed to quantify variations in the acoustic signal from three perceptual aspects, including articulation, prosody, and vocal quality. The developed measures have been validated on a dysarthric speech dataset with various severity degrees. Multiple regression analysis is employed to show the developed measures could predict perceptual ratings reliably. The relationship between the acoustic measures and the listening errors is investigated to show the interaction between speech production and perception. The hypothesize is that the segmental phoneme errors are mainly caused by the imprecise articulation, while the sprasegmental lexical boundary errors are due to the unreliable phonemic information as well as the abnormal rhythm and prosody patterns. To test the hypothesis, within-speaker variations are simulated in different speaking modes. Significant changes have been detected in both the acoustic signals and the listening errors. Results of the regression analysis support the hypothesis by showing that changes in the articulation-related acoustic features are important in predicting changes in listening phoneme errors, while changes in both of the articulation- and prosody-related features are important in predicting changes in lexical boundary errors. Moreover, significant correlation has been achieved in the cross-validation experiment, which indicates that it is possible to predict intelligibility variations from acoustic signal.
ContributorsJiao, Yishan (Author) / Berisha, Visar (Thesis advisor) / Liss, Julie (Thesis advisor) / Zhou, Yi (Committee member) / Arizona State University (Publisher)
Created2019