A cineradiographic study of speech production.

Abstract

The ability to speak is a distinctly human characteristic, and is probably the most complex sensory-motor activity in which man engages. The need to understand more about this process is urgent, and any technics which may shed light upon it should be investigated. In speaking, the sound produced at the level of the larynx is modified primarily by the structures in the oral region: the tongue, the velum palatinum, the alveolar ridge, and the teeth. To the person speaking, the senses of hearing and touch provide important information. These forms of feedback let the speaker know, through auditory and physiologic stimuli, how he is doing and enable him to regulate specific movements of the articulators. The relationship of the various oral structures to one another during the process of speech has been studied in a variety of ways. For example, one may look at the person speaking and make certain observations regarding these relationships. Obviously, there are limitations to this method. Or, through the use of palatograms, observations may be made in respect to the site at which the tongue makes contact with the palate in producing sounds. This technic, however, is a static one and does not yield information relative to the sequence of movements involved. Cinefluorographic studies have been made of normal speech production and afford an opportunity to view speech structures not normally amenable to visual inspection, and to view them in action. The exploratory study to be described here was designed to investigate the influence of reduced auditory and tactile feedback on compensatory articulatory movements. Because of the advantages of the cineradiographic technic, it was selected for this investigation. Method To test the role of some of the feedback mechanisms, we attempted to block their paths, individually and in combination. Eleven normal young adult males with no detectable speech abnormality or oral pathologic condition were used in an experiment with four selected phonemes. Each subject spoke the phonemes in isolated form and in combination with other phonemes to form words. Our phrases were: Th as in thoughts Ss as in sots T as in tots D as in dots As the subject recited these phrases, his tongue action was roentgenographed by a cineradiographic strip from a Philips 5-inch image amplifier, and his voice was simultaneously recorded on tape. During the tests a wooden tongue blade was inserted vertically between the jaws. Small notches were cut in the upper and lower margins, 25 mm. from the end, in which upper and lower central incisor teeth were placed during the test to immobilize the jaws and interfere with normal tongue action. The mechanical difficulty encountered by the subjects in speaking with this impediment caused them to engage in compensatory articulatory movements.