Carrie Niziolek, Ph.D.
Assistant Professor in the Department of Communication Sciences and Disorders
Increased vowel contrast in connected speech induced by sensorimotor adaptation
Alterations to sensory feedback can drive robust adaptive changes to the production of consonants and vowels, but these changes often have no behavioral relevance or benefit to communication effectiveness (e.g., causing “head” to be more similar to “had”). This work aims to align the outcomes of adaptation with changes known to increase speech intelligibility. Specifically, we target adaptations that would increase speakers’ working vowel space area and increase the acoustic contrast between vowels in running speech. To this end, we implemented a vowel centralization feedback perturbation paradigm that pushes all vowels towards the center of the vowel space, making them sound less distinct from one another. Speakers adapted to the centralization perturbation during sentence production, increasing their working vowel space for connected speech, as defined by the global articulatory-acoustic vowel space (AAVS) measure. These changes partially persisted after the feedback shift was removed, including after a 10-minute silent period. Additionally, this learning showed a robust transfer to isolated monosyllabic words that were not present in the sentence stimuli. These findings establish the validity of a sensorimotor adaptation paradigm to increase vowel contrast in connected speech, an outcome that has the potential to enhance intelligibility in individuals who present with a reduced vowel space due to motor speech disorders, such as the hypokinetic dysarthria associated with Parkinson’s disease.