Speech Motor Control from a Modern Control Theory Perspective
Spoken language exists because of a remarkable neural process. Inside a speaker’s brain, an intended message gives rise to neural signals activating the muscles of the vocal tract. The process is remarkable because these muscles are activated in just the right way that the vocal tract produces sounds a listener understands as the intended message. What is the best approach to understanding the neural substrate of this crucial motor control process? One of the key recent modeling developments in neuroscience has been the use of state feedback control (SFC) from modern engineering control theory to explain the role of the CNS in motor control. SFC postulates that the CNS controls motor output by estimating the current dynamic state of the thing (e.g., arm) being controlled and by generating controls based on this estimated state. SFC has successfully predicted a great range of nonspeech motor phenomena, but as yet it has not received attention in the speech motor control community. Here, we review some of the key characteristics of speech motor control and what they say about the role of the CNS in the process. We then discuss prior efforts to model the role of CNS in speech motor control and argue that these models can be considered variations of an SFC model of speech motor control which we describe. We conclude by discussing a plausible neural substrate of our model.