Kinematic analysis of tongue movements in dysarthria following traumatic brain injury using electromagnetic articulography

Electromagnetic articulography (EMA), a technique that uses alternating magnetic fields to track the movement of miniature receiver coils affixed to the articulators, was used to assess the speed and accuracy of tongue movements exhibited by an individual with dysarthria following severe traumatic brain injury (TBI). Three receiver coils were attached to the TBI subject's tongue and the movements of these coils were recorded during five productions of three single syllable real words consisting of the lingual consonants /t, s, k/ in the word-initial position. A non-neurologically impaired adult male served as a control subject. A range of kinematic parameters was analysed from the consonant productions including the movement trajectories, velocity, acceleration, distance, and duration of tongue movements. Examination of the complex interactions between the kinematic parameters recorded for the TBI subject revealed a disturbance in the 'control' of tongue speed rather than a disturbance in speed per se, as it was found that the TBI subject exhibited difficulty in decelerating his tongue movements appropriately on the approach up to the palate during consonant production. The difficulty noted in deceleration resulted in inaccurate tongue movements that overshot the point of intent (in the case of /t/) and may have been instrumental in reducing the length of time that the tongue remained at the palate (in the case of /s/ and /k/) in comparison to the control subject. The disturbances identified in the kinematic parameters recorded provided objective insights into the nature of the articulatory disturbances responsible for the deviant speech feature, consonant imprecision, perceived in the TBI subject's speech. The study stresses the importance of examining a range of kinematic parameters and the interactions between these parameters in attempting to determine the nature of articulatory disturbances exhibited by individuals with dysarthria following TBI.