Effect of speech loudness manipulations on articulatory dynamics in severe traumatic brain injury

Abstract

BackgroundAlteration of speech loudness is an important component of the treatment of dysarthria aimed at improving speech intelligibility and/or naturalness of speech.ObjectiveTo determine the effects of manipulations of speech loudness (habitual vs. loud) on lingual kinematics and tongue-to-palate contacts in adult speakers with severe traumatic brain injury (TBI) and matched normal controls.Materials and methodsSix adults with severe TBI and five matched non-neurologically impaired controls underwent testing of their articulatory function using electromagnetic articulography and electropalatography (EPG).ResultsLoudness-related scaling of articulatory movements was observed in both the control and TBI groups for speech tasks that demonstrated a significant magnitude of loudness change in the absence of any reduction in speech rate. The TBI group demonstrated these effects during sentence production and during repetition of velar syllables. In contrast, the control group only exhibited an upscaling of articulatory movements for loud speech during repetition of alveolar syllables. Although the TBI group was significantly louder for all tasks than the control group, they also exhibited a significant decrease in overall speech rate compared to controls during sentence production at the loud level. Articulatory kinematics during loud speech production was comparable between the two groups. EPG results indicated no significant difference between the control and TBI groups for the loud condition on the temporal aspects of tongue-to-palate contact. The TBI group did show a significantly greater number of EPG contacts than controls during repetition of velar syllables.ConclusionsAlthough the TBI group differed to controls in loudness level and overall speech rate, their articulatory kinematics during loud speech were comparable. It is possible that upscaling of articulatory movements associated with increased loudness may have been offset by the downscaling of articulatory movements associated with reduced rate of speech.