The impact of reduced speaking rate on velopharyngeal functioning

Human speech is a complex motor activity involving the coordination of multiple structures. Through practice, individuals develop a set of rules, or speech motor schema, which allows coordination of these multiple structures. Once the rules and the speech goal are known, speakers modify parameters such as rate, amplitude, and duration of a movement to achieve the desired speech outcomes. Manipulation of these parameters has been used clinically to improve speech intelligibility for speakers with dysarthria. However, little is known regarding the impact of reduced speaking rate on maintaining the stability of motor performance. In this study, fifteen individuals with no known history of neurological disorder attempted speaking tasks under four controlled speaking rate conditions. The speakers produced a grammatically correct sentence, Buy Bob a pie , an agrammatical sentence, Pie Bob a buy and a syllable string, papapa , at the speaker\u27s habitual, or typical speaking rate, and then at three reduced speaking rates. These productions were recorded aerodynamically using AEROWIN, a Windows-based acquisition and analysis system. The investigator then completed aerodynamic and pattern analysis on these productions. Responses were categorized into one of four patterns: (1) expected, (2) end of utterance, (3) schema, and (4) mixed. The expected and end of utterance patterns indicated no breakdown in the motor schema, whereas occurrence of the schema and mixed patterns were reflective of a motor schema breakdown. Results indicated an increase in unexpected patterns as speaking rate was decreased. The highest frequency for unexpected patterns was typically noted at speaking rates which were approximately 30 to 40% slower than the habitual speaking rate. Based on these findings, reduced speaking rate does appear to impact velopharyngeal functioning. This may be related to a breakdown in the motor schema when speakers must reduce the parameter of rate. Further research involving speakers with dysarthria is necessary