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- Creators: Daliri, Ayoub
Description
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
Description
Speech sound disorders (SSDs) are the most prevalent type of communication disorder in children. Clinically, speech-language pathologists (SLPs) rely on behavioral methods for assessing and treating SSDs. Though clients typically experience improved speech outcomes as a result of therapy, there is evidence that underlying deficits may persist even in individuals who have completed treatment for surface-level speech behaviors. Advances in the field of genetics have created the opportunity to investigate the contribution of genes to human communication. Due to the heterogeneity of many communication disorders, the manner in which specific genetic changes influence neural mechanisms, and thereby behavioral phenotypes, remains largely unknown. The purpose of this study was to identify genotype-phenotype associations, along with perceptual, and motor-related biomarkers within families displaying SSDs. Five parent-child trios participated in genetic testing, and five families participated in a combination of genetic and behavioral testing to help elucidate biomarkers related to SSDs. All of the affected individuals had a history of childhood apraxia of speech (CAS) except for one family that displayed a phonological disorder. Genetic investigation yielded several genes of interest relevant for an SSD phenotype: CNTNAP2, CYFIP1, GPR56, HERC1, KIAA0556, LAMA5, LAMB1, MDGA2, MECP2, NBEA, SHANK3, TENM3, and ZNF142. All of these genes showed at least some expression in the developing brain. Gene ontology analysis yielded terms supporting a genetic influence on central nervous system development. Behavioral testing revealed evidence of a sequential processing biomarker for all individuals with CAS, with many showing deficits in sequential motor skills in addition to speech deficits. In some families, participants also showed evidence of a co-occurring perceptual processing biomarker. The family displaying a phonological phenotype showed milder sequential processing deficits compared to CAS families. Overall, this study supports the presence of a sequential processing biomarker for CAS and shows that relevant genes of interest may be influencing a CAS phenotype via sequential processing. Knowledge of these biomarkers can help strengthen precision of clinical assessment and motivate development of novel interventions for individuals with SSDs.
ContributorsBruce, Laurel (Author) / Peter, Beate (Thesis advisor) / Daliri, Ayoub (Committee member) / Liu, Li (Committee member) / Scherer, Nancy (Committee member) / Weinhold, Juliet (Committee member) / Arizona State University (Publisher)
Created2020