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Studies of speech production and its control have traditionally focused on acoustic parameters and/or articulatory configurations of the end result of the production process as the target of speech production. The representations of production target, however, are far richer than the stereotypical acoustic/articulatory features that have been identified from those traditional studies. Speech production is a process through which mental representations of a language are transformed into vocal tract movements and sounds as physical entities. Thus, the speech production target includes these complete representations, and in order to fully understand how the target is controlled, we need to perturb the production process. This paradigm allows us to see how the production system as a whole corrects behavior in response to the perturbation. By systematically introducing perturbation, it is possible to examine what is needed for the system to detect an error, and how such an error is reduced. This, in turn, enables us to have a better understanding of what the speech production target is and how it is defined. A series of experiments were carried out to examine this issue in this thesis, using a real-time auditory perturbation paradigm. This paradigm perturbs the auditory feedback speakers receive while they are producing a speech segment. In response to the perturbation, subjects spontaneously change their articulation to compensate. The results showed that 1) the speech production target is not a list of independently controlled acoustic features but is a multi-dimensionally defined category that is language dependent 2) spectral and temporal aspects of speech motor control show the same results 3) similar compensation behavior is observed even with using an unfamiliar tool to produce a vowel-like sounds, and 4) an intention to produce a speech category may be manifested in ways that are different than behavior in other motor control studies such as reaching. / Thesis (Ph.D, Psychology) -- Queen's University, 2013-09-30 22:44:48.165

One enduring question in the study of speech concerns the nature of the link between speech perception and production. Although accumulating evidence suggests that these two facets of spoken language are tightly coupled, the cognitive structure and neural organization underlying the interactions between the two processes are not well understood. In this thesis, I focus on questions that arise from observations related to when individuals are both talking and listening, and assess the sensitivity of talkers and listeners to the same change in the acoustics of speech. First, I aim to elucidate the neural substrates of auditory feedback control during vocalization by examining the brain response to acoustic perturbations towards auditory concomitants of speech using functional magnetic resonance imaging (fMRI) (Chapters 2 and 3). I demonstrate, for the first time, an extensive network of brain regions involved in the detection and correction of auditory feedback errors during speech production, for which three functionally differentiated neural systems can be delineated. Then I set out to address the online perception of own voice identity as individuals are talking. Chapters 4 and 5 measure the perceptual sensitivity of individuals to the auditory concomitants of their own speech by presenting temporally gated auditory feedback in stranger’s voices during talking. The results show that people perceive stranger’s voices as a modified version of their own voice and adjust their vocal production accordingly, when their utterances and heard feedback are phonetically congruent. Chapter 6 further examines this perceptual effect by using experimental paradigms in the domain of body ownership and shows that the misattribution of the stranger’s voice, is not predicted by individual differences in suggestibility; rather it is related to the integration of multimodal cues. In summary, by focusing on how the acoustics of speech are simultaneously processed for both the perception and production sides of spoken language, the series of studies add significantly to our understanding of the psychophysical, cognitive and anatomical relationships between speech perception and production, and are relevant to a wide range of clinical pathologies (e.g., stuttering, schizophrenia). / Thesis (Ph.D, Neuroscience Studies) -- Queen's University, 2012-08-29 10:08:57.516

Previous research has demonstrated that normally developing children are expected to have adult like control of their speech production skills by 10 years of age, as evidenced by increases in speed of production and decreases in performance variability. (e. g. Kent and Fortier 1980). There is also some evidence to suggest that phonologically disordered children may have poorer speech motor skills than their normally developing peers (e. g. Henry 1990, Edwards 1992, Waters 1992, Towne 1994). There are numerous techniques that can be used to measure a number of different aspects of speech motor control. However, there are methodological difficulties in devising appropriate protocols for the collection and analysis of speed of speech production as used as an index of speech motor skill in young children. Some of the techniques that have had clinical application include measurement of rate in connected speech production and measurement of diadochokinetic (DDK) repetition rate. This investigation compared normally developing and phonologically disordered preschool children on various indirect measures of speech motor skills, in imitated and spontaneous connected speech and in DDK tasks. The investigation also focused on refining the techniques of data collection and analysis appropriate to young children. While the results vary with regard to the statistical significance of the differences between the two groups of children on articulation rates and DDK rates, analysis of the error patterns in single word, spontaneous connected speech, imitated connected speech and DDK productions identified a sub group of phonologically disordered children who may present with an underlying speech motor deficit as the basis of their phonological disability. The results of the investigation are considered in terms of their implication for the speech motor skills of the two groups of children, techniques for measuring various aspects of speech motor skill and the clinical identification of phonologically disordered children who have an underlying speech motor deficit.

Det har tidigare rapporterats att icke-stammande personer har en tydlig vänstersidig cerebral lateralisering vad gäller talmotoriken, vilket visas genom ökad högersidig aktivering i läppmuskulaturen. Personer med stamning har å andra sidan föreslagits ha ett vänstersidigt eller bilateralt aktiveringsmönster av talmuskulaturen. Detta antas vara en av orsakerna till stamning. Testdeltagarna i aktuell studie bestod av 11 stammande och 13 matchade icke-stammande vuxna. Uppgifterna bestod av ordrepetition, ordgenerering samt att puta med läpparna. EMG-aktivitet från musklerna orbicularis oris och depressor labii inferior registrerades med elektroder på höger och vänster sida av läppmuskulaturen. Syftet med aktuell studie var att undersöka eventuell skillnad i läppasymmetri mellan stammande och icke-stammande vuxna personer. Resultatet kunde inte påvisa signifikanta gruppskillnader i grad av muskelaktivering för läppmuskulaturen. Båda grupperna uppvisade tvärtemot förväntan en nästintill bilateral aktivitet. En tendens till positiv korrelation, om än inte statistiskt signifikant, kunde observeras mellan grad av uppvisad stamning och något mer högersidig muskelaktivering.

This study investigated the effect of palate morphology and anthropometric measures of the head and face on lingual consonant target (positional) variability of twenty one adult speakers (eleven male, ten female). An electromagnetic tracking system (WAVE, NDI, Canada) was used to collect tongue movements while each speaker produced a series of VCV syllables containing a combination of consonants /t, d, s, z, ʃ, tʃ, k, g, j/ and three corner vowel /i, ɑ, u/. Distributions of x, y, and z coordinates representing maximum tongue elevation during the consonants were used to represent target variability across contexts. Palate and anthropometric measures were obtained for each participant. A correlational analysis showed that target variability of the consonants produced in the front of the mouth (e.g. alveolar and palatal) was explained, to a degree, by palate morphology. The variability of velar consonants was not explained by the structural measures.

This study investigated the effect of palate morphology and anthropometric measures of the head and face on lingual consonant target (positional) variability of twenty one adult speakers (eleven male, ten female). An electromagnetic tracking system (WAVE, NDI, Canada) was used to collect tongue movements while each speaker produced a series of VCV syllables containing a combination of consonants /t, d, s, z, ʃ, tʃ, k, g, j/ and three corner vowel /i, ɑ, u/. Distributions of x, y, and z coordinates representing maximum tongue elevation during the consonants were used to represent target variability across contexts. Palate and anthropometric measures were obtained for each participant. A correlational analysis showed that target variability of the consonants produced in the front of the mouth (e.g. alveolar and palatal) was explained, to a degree, by palate morphology. The variability of velar consonants was not explained by the structural measures.

This thesis presents evidence from a formant perturbation experiment which supports the hypothesis that speech targets are multimodal. A real-time auditory feedback perturbation is used to gradually shift English speakers' formants from the vowel /E/ towards /I/. Most speakers compensate at the level of acoustics, adjusting their production towards /ae/ such that they hear themselves producing the correct vowel. Subjects' articulation is tracked with electromagnetic-articulography. The articulatory data shows that subjects tend to produce marginal /E/s at the level of articulation - remaining within the normal articulatory bounds for that vowel, while adjusting the position of individual articulators to a sufficient extent to create an acoustic compensation to the perturbation. The higher-order relationship between speed and curvature is shown to differ across different vowel phonemes. However, this measure remains constant under formant perturbation. These findings are argued to show that phonemic targets are multi-modal, having acoustical, kinematic, and dynamic components.

This thesis presents evidence from a formant perturbation experiment which supports the hypothesis that speech targets are multimodal. A real-time auditory feedback perturbation is used to gradually shift English speakers' formants from the vowel /E/ towards /I/. Most speakers compensate at the level of acoustics, adjusting their production towards /ae/ such that they hear themselves producing the correct vowel. Subjects' articulation is tracked with electromagnetic-articulography. The articulatory data shows that subjects tend to produce marginal /E/s at the level of articulation - remaining within the normal articulatory bounds for that vowel, while adjusting the position of individual articulators to a sufficient extent to create an acoustic compensation to the perturbation. The higher-order relationship between speed and curvature is shown to differ across different vowel phonemes. However, this measure remains constant under formant perturbation. These findings are argued to show that phonemic targets are multi-modal, having acoustical, kinematic, and dynamic components.

This study examined the impact of several noise conditions on speech articulator movements during a sentence repetition task. Sixty participants in three age groups ranging from 20 to 70 repeated a sentence under five noise conditions. Lower lip movements during production of a target sentence were used to compute the spatiotemporal index (STI). It was hypothesized that STI would be lower (indicating greater stability) in the silent baseline condition. There were changes in speech production under several of the noise conditions. The duration for the 1-talker condition was significantly shorter when compared to the silent condition, which could be due to the impact of the 1-talker noise on the attention of the speaker. The peak velocity of a selected closing gesture increased in all of the noise conditions compared to silence. It could be speculated that the repetitive and predictable nature of the speaking task allowed participants to easily filter out the noise while automatically increasing the velocity of lip movements, and consequently, the rate of speech. The STI in the pink noise and 6-talker conditions was lower than in the silent condition, which may be interpreted to reflect a steadier manner of speech production. This could be due to the fact that in the 6-speaker noise condition, the overall effect was more similar to continuous noise, and thus potentially less distracting than hearing a single speaker talking. The count of velocity peaks was unexpectedly lower in the noise conditions compared to speech in silence, suggesting a smoother pattern of articulator movement. The repetitiveness of the task may not require a high level of self-monitoring, resulting in speech output that was more automatic in the noise conditions. With the presentation of noise during a speaking task, the intensity increased due to the Lombard effect in all of the noise conditions. People communicate in noisy environments every day, and an increased understanding of the effects of noise on speech would have value from both theoretical and clinical perspectives.