ABSTRACT
This chapter discusses clinical and experimental evidence for a task-specific organisation of the speech motor system. The motor actions of the facial—oral—laryngeal—respiratory musculature are classified by two criteria, i.e., voluntary vs. involuntary and learned vs. novel. A review of the literature on the dysarthrias and apraxia of speech reveals that separate organisational principles and separate neural substrates exist for different types of oral motor activities. Focussing on speech vs. voluntary nonspeech motor control, it is postulated that extensive motor learning leads to the emergence of a specific neural circuitry for the control of articulation. Indirect evidence for this view is provided by analogies from studies of sequential finger movement learning and tool-use learning. The “vertical” view of speech motor control proposed here has important theoretical and clinical implications.
