Cognitive Motor Constraints and Motor Speech Disorders: A Preliminary Framework
The role of cognitive constraints in movement is reviewed as a foundation for the argument that they have been largely ignored in the Mayo Classification of dysarthria. The classification being inspired by a medical model, has only given consideration to the perceptual implications of system constraints, i.e., weakness and/or incoordination in the speech musculature. An unintended consequence of conceiving the dysarthrias this way is that these speech disorders therefore must be impervious to cognitive or any context for that matter. Another implication is that the classification system, to be internally consistent, cannot but categorize the dysarthrias and other “motor” speech disorders that occur in the setting of neurogenic cognitive disturbances as different leaving little opportunity to comment on the relation that exists between these speech disorders. In light of these considerations, a prosodic framework will be presented that specifies cognitive constraints in speech in terms of intrinsic and extrinsic prosody while not ignoring system properties. The proposed frame-work is intended to complement, not replace the Mayo classification, so that the relation (overlap) between disorders such as apraxia of speech, stuttering, aprosody, hypokinetic dysarthria, and ataxic dysarthria can better be addressed.