Characterizing covert articulation in apraxic speech using real-time MRI

We explore the use of real-time magnetic resonance imaging (rtMRI) as a tool to investigate apraxic speech, in particular, by examining articulatory behavior. Our pilot data reveal that covert (silent) gestural intrusion errors (employing an intrinsically simple 1:1 mode of coupling) are made more frequently by an apraxic subject than by fluent speakers. Covert intrusion errors are also found to be pervasive in non-repetitious apraxic speech. We demonstrate that acoustically silent periods observed before the initiation of apraxic speech oftentimes contain completely covert gestures that occur frequently with multigestural segments. Covert gestures corresponding to entire words are also observed. These data demonstrate that rtMRI can provide important new insights into apraxic speech that are not available using traditional methods of transcription based on acoustic data alone.