Dysarthria in traumatic brain injury: A breath group and intonational analysis

Prosodic abnormality is a common feature in the dysarthrias associated with traumatic brain injury (TBI), but very few analytic studies have been reported on the nature of the prosodic disturbances. This study, based on analyses of conversational and sentence speech samples, reports on breath group structure and its temporal and intonational components for 12 subjects with TBI and 8 healthy controls. It introduces the method of f₀ close-copy stylization to the study of intonational patterns in dysarthria. The subjects with TBI had reduced mean length and variation of breath groups along with frequent inappropriate locations of breath pause and lengthy and variable breath pauses. Prosodic features that were preserved in the subjects with TBI were phrase final lengthening, f₀ down-trend and a relatively normal f₀ distribution. However, these subjects had reduced speaking and articulation rates, reduced f₀ movement and reduced f₀ slope. The phrase final lengthening and f₀ downtrend phenomena, which can serve as prosodic cues of syntactic boundary, appear to be robust features of speech production, but the dynamic features of f₀ control were more vulnerable to the neurological damage. This study indicates the importance of breath group management in TBI-induced dysarthria and the need to use methods such as those used in this study for large-scale investigations that examine cognitive, linguistic and motoric factors that conspire to reduce communicative efficiency.