this area where you have a stronger signal being sent to the brain. There is a maintenance factor for tongue thrust from sensory feedback or from motor-sensory interactions. The primitive neuromotor response is to protrude or retract itself. Children who cannot elevate the tongue tip well will tend to persist in tongue thrusting as their neuromotor systems lag in development, so there is a neuromotor component to the maintenance of the tongue thrust.

DR. SHIPMAN: Dr. Mason, you hinted in your presentation that advanced periodontal disease and the lack of papillae and so on can compromise respiratory sufficiency, that the use of the tongue will then accomodate to the situation and you classified it as a tongue thrust. Had you related the end state of periodontal disease, that is edentulousness, and the construction of complete dentures and position of the tongue with complete dentures in any relationship to tongue thrusting in children, as a chronology or advancement of the problem?

DR. MASON: I'm not sure I even understand the statement, but I hope I did not say that tongue thrust as seen in patients is related to respiration. I'm simply saying that when there is a cumulative open bite, as I call it, created in front of the mouth, the tongue will come forward to seal off that area during swallowing, so I'm not trying to tie it up with respiration. But in terms of dentures, any of us who went to dental school learned a lot of principles about the freeway status that were based on the edentulous patient. And something that we do not see in people with teeth--they never clack against their teeth when they are talking. There is something in the periodontal ligaments that is able to control and mediate as far as adaptation to the freeway space. So I don't know how to answer that question particularly. I'm just trying now in my own mind to separate out what I was taught in dental school about some principles of oral biology that were based on the edentulous and now try to come up with some different things.

DR. SHIPMAN: In constructing dentures, the position of the tongue is critical for a stable mandibular denture. Might there be any correlation between children who have a tongue thrust--whether a positive or negative habit--and the relationship, as in an older adult to the position of their tongue with the construction and use of complete dentures--whether we're dealing with tongue thrusting mostly as a childhood or young adult problem, and not looking at the other end of the spectrum. I wonder if there isn't some correlation.

DR. MASON: I don't know the answer to that, although I do know there are many normal children and adults with tongue thrust who have no clinical problems with it, no malocclusion or speech problems. How that works out in the edentulous mouth is a very good question. I have no idea. Maybe speculation at that point would simply have to be "tongue in cheek.'

DR. GALE: I'll close this subject with a comment. It appears important in both areas we've covered this morning to look at longitudinal effects. With bruxism and tongue thrust in children, how does this affect the adult?

What are the progressive relationships? Whether in fact some of the adults you see may have developed this as a later behavior, or whether this is a continuation. The need Dr. Popovich expressed for longitudinal studies in this area becomes apparent.

Conceptualizing Oral Motor Behavior: An Examination of the Cognitive and Control Aspects

George E. Stelmach

A necessary and often elusive goal of the motor behaviorist is to discover the behavioral laws and principles underlying human learning and performance, eventually providing practitioners with a rationale for producing optimal motor behavior and correcting dysfunction in every individual. This goal, shared by researchers in many fields, presents four barriers to be crossed: (1) research, (2) development, (3) dissemination, and (4) implementation. The emphasis of the present paper will be on conceptualizing the nature of orofacial behavior via examination of the pertinent literature in cognitive psychology and motor control areas. Hopefully, presenting such information pertaining to motor behavior will provide insight and a better conceptual understanding of how to deal with normal and dysfunctional orofacial motor behaviors.

Diagnosis of oral motor disorders is a professional skill. The basic goals of the diagnostician are to discover the patient's motor problem, understand the potential causes of the problem, and propose appropriate treatment recommendations. To accomplish these goals the dental clinician must have a basic knowledge of normal and disordered oral motor behavior, organize this information into a conceptual framework, and understand the methodology necessary for solving the problem.

Most of you are familiar with many types of oral motor behaviors and their dysfunctions such as normal speech and chewing, improper bites, malocclusions and orofacial imbalances, but have perhaps not thought too much about the underlying processes or mechanisms that regulate these behaviors. The learning of motor behaviors involves the integration of efficient strategies within the control of an everchanging human behaving system.

The scientific method as adapted to the clinical process should be the diagnostician's major tool. The scientific orientation to diagnosis allows clinicians to pursue diagnosis as a problem-solving process with the goal of understanding the nature, extent, and consequences of oral motor disorders. For some, oral motor behaviors may be thought of as a special response class of motor skills, but the theme of this paper will be such that these motor behaviors are not very different from the complex motor activities performed with other body segments (walking, writing, striking) in daily life. I would like to contend that oral motor behaviors are simply motor skills, and dental medicine has much to gain by examining the current state of the art in the motor control and learning area.

Cognitive Aspects of Oral Motor Behavior

It has been traditional to view oral motor behavior in terms of a "black box," a term adapted from the physical sciences to designate areas of a system in which it is not known exactly what is taking place. This view describes input and output with little attention paid to what goes on inside the brain. The black box approach of oral motor behavior handles internal processes by simply ignoring them. The central nervous system that regulates oral behaviors is viewed as an impenetrable black box receiving inputs (stimuli) and emitting outputs (responses) where associations (habits) determine the quality and persistance of the motor behavior. While in the past these types of studies were popular, this was the extent to which researchers went in conceptualizing the nature of oral motor behavior. Without information about intervening mechanisms and with little in the way of theoretical orientation, most early oral motor behavior research contributed little toward the understanding of normal and dysfunctional motor behavior.

I would like to introduce an approach to skill learning that examines the mental operations that intervene between perception and oral motor behaviors. The central tenet of this information processing approach is that in motor behavior there are a number of mental operations which are performed by the patient to solve a particular problem or perform a task. Information processing attempts to examine the role of the control system in sensing, attending to, transforming, retaining, and transmitting information. The appealing aspect of this approach is that it focuses attention on the cognitive activities that precede oral motor acts which are often neglected, and provides a rationale for linking cause and effect relationships during examinations. The point is that an individual continually processes information from all modalities and actively operates on it to transform it for a particular use. Patients continuously register, process and respond to a variety of stimuli such as pain, perturbations, movements or speech sounds. With a little thought, it is easy to realize that a great deal must go on between cognition and the execution of motor acts. What goes on during this interval is actually a complex series of events that we are hardly aware of.

What sort of alternatives does an information processing approach offer practitioners that work with oral motor behavior? It provides a way of understanding many problems that might otherwise remain unclear. An information processing model may be used to propose descriptions for the contents of the impenetrable black box, such as viewing the transformation of information as a continuum, linked by a series of complex researchable processes such as perception, memory, response execution, and feedback. Therefore, diagnosis is a far different skill than just learning a series of testing procedures applicable to specific oral motor disorders. Massaro (1975) states that "the information processing methodology can be thought of as a microscope." It allows us to see

what is not directly observable. Similarly it serves in a heuristic capacity permitting the integration of experimental and diagnostic results in some coherent manner from many different sources. Thus it functions as an organizational medium and imposes consistency in methodology, interpretations and conclusions.

Another reason for adopting the information processing approach is that it enables the clinician to view the patient as an active processor, not just a passive recipient of stimulation, discomfort therapy. Employment of the information processing approach allows us to compare the ways in which different aspects of behavior are structured in memory, so that common properties can be discussed. Finally, the process-oriented approach is used because it provides a means to describe as precisely as possible the many separate steps, stages and mechanisms that a typical patient experiences.

It is obvious that if dental medicine is to advance, there needs to be a better understanding of the numerous and complex problems associated with oral motor behavior. Since the clinicians must mediate between the patient and the dysfunction when providing corrective experiences it is important that they can conceptualize the nature of oral motor behavior. It is this knowledge that will allow the practitioner to prescribe rational, meaningful activities that rehabilitate the patient through sound, useful procedures. Unlike the black box approach which views only the behavioral products, the cognitive approach to motor behavior stresses a complete conceptualization of behavior through the description of the precise mental operations that are associated with motor acts.

The definition and dissection of stages of processing should not bered the major contribution of the approach. I believe its usefulness as a framework for conceptualizing oral motor behavior is the greatest benefit to dental medicine. It successfully focuses the clinician's attention on underlying processes, allowing more effective analyses of specific oral dysfunctions. The practitioner who understands the processes that underlie motor behavior is aware of the patient's probable cognitive strategies in situations of discomfort or dysfunction. This awareness, coupled with an understanding of the functional components of specific motor behaviors and their requisite demands, increase the capacity of the practitioner to diagnose motor problems. The practitioner should be able to identify more accurately the source of perceptual-motor deficits. Thus, the delineation of patient and orofacial behavior transforms the communicative interaction between clinicians and patient from vague suggestions to articulate directions. Once problems have been diagnosed, the information processing concept aids the practitioner in developing prescriptive judgments toward solutions.