Contact of the tongue against the hard palate plays an important role in swallowing. This study aimed to clarify the pattern of contact between the tongue and hard palate by analyzing tongue pressure produced in swallowing 15 ml of water by healthy subjects wearing an experimental palatal plate with seven pressure sensors. Tongue pressure was generated initially by close contact with the anteriomedian part of the hard palate, then with the circumferential part, and finally softly with the posteriomedian part. Tongue pressure reached a peak quickly, then decreased gradually before disappearing almost simultaneously at each measured part of the hard palate. Magnitude and duration were significantly larger in the anteriomedian part compared to the other six parts measured, and was significantly smaller in the posteriomedian part. No laterality was found in tongue pressure produced at the circumferential parts of the hard palate. Our findings indicate that the order of tongue contact against each part of the hard palate as well as duration and magnitude of tongue pressure are coordinated precisely during swallowing. These findings could aid assessment of the tongue movement of dysphagic patients during rehabilitation.

This system could be useful for evaluating tongue activity during oropharyngeal swallowing.

An in vitro evaluation system of food texture was developed using artificial tongue and a conventional uniaxial compression apparatus to mimic the tongue-palate compression. Deformation behavior of agar gels on artificial tongues from silicone rubber with three levels of elastic modulus was observed during compression by a nondeformable plate. The results were compared with the oral strategy for size reduction from sensory evaluation by human subjects. Agar gels fractured upon compression when the strain of the gels was larger than that of artificial tongue, whereas they did not when the strain of the gels was equivalent to or smaller than that of the artificial tongue. When apparent elastic modulus of artificial tongue was approximately 5.5 ¥ 10 4 Pa, fracture profile of the gels corresponded well to human tests. Results suggest that the oral strategy for size reduction might be determined by sensing the relative strain of the gels to the tongue during compression to a somewhat small strain.

Measurement of the magnitude of tongue pressure shows promise as a simple, non-invasive and quantitative method by which tongue activity in post-stroke patients, in whom swallowing ability is a concern, could be evaluated.

The tongue plays an important role in mastication and swallowing by its contact with the hard palate. Using an experimental palatal plate with 7 pressure sensors, and recording jaw movement using mandibular kinesiography, we assessed, in healthy subjects, the coordination of tongue and jaw movements during the entire masticatory sequence of solids, by measuring tongue pressure against the hard palate. Tongue pressure appeared during the occlusal phase, reached a peak near the start of opening, and disappeared during opening. Specific patterns in order, duration, and magnitude of tongue pressure were seen at the 7 pressure sensors in each chewing stroke. Magnitude and duration were significantly larger in the late stage of chewing (8 strokes before initial swallowing) than in the early stage (until 8 strokes after starting mastication). The normal pattern of tongue contact against the hard palate, control of tongue activity, and coordination with jaw movement during mastication is described.

Background: Although poststroke dysphagia is an important issue for determining prognosis, the pathophysiology of oral-phase dysphagia has yet to be clarified due to a lack of adequate devices and protocols. The present study investigated the relationships between swallowing pressure production by the tongue and dysphagia in stroke patients using a newly developed method of tongue pressure measurement with a sensor sheet system. Methods: Subjects were 64 stroke patients, including 30 patients with dysphagia. A T-shaped sensor sheet with 5 measuring points was attached to the hard palate to record tongue pressure while swallowing 5 ml of water. The average maximal magnitude and incidence of abnormalities such as asynchronous and/or polyphasic patterns in tongue pressure waves in 5 locations were compared between patients with and without dysphagia. Results: The average maximal tongue pressure was significantly smaller in patients with dysphagia than in those without dysphagia. Asynchronous and polyphasic patterns showed a sensitivity of 63 and 87%, and a specificity of 91 and 71%, respectively, for identifying patients with dysphagia. Conclusion: Tongue pressure production during swallowing appears closely related to poststroke dysphagia. Tongue pressure measurement appears useful for evaluating the pathophysiology of oral-phase dysphagia in stroke patients.

Instrumental compression test using artificial tongue was carried out to compare the fracture profile of gels with the first oral strategy for size reduction by humans (termed as the first size reduction). Gellan gel samples, whose size and shape were the same as those of artificial tongue, were prepared in a wide mechanical range and were compressed uniaxially on artificial tongue at crosshead speed of 10 mm/s. When apparent Young's modulus of artificial tongue was approximately 55 kPa, fracture probability of gels corresponded to the ratio of subjects who decided to use tongue‐palate compression instead of mastication. This was applicable to the gels whose fracture strain was below 65% but not to the gels whose fracture strain was above 70% within the range of fracture stress tested; approximately 30–100 kPa. Fracture strain should be a critical initial mechanical parameter that relates to the decision of oral strategy. Practical Applications There is an increasing demand for texture‐controlled foods that can be consumed by tongue‐palate compression without the need of mastication as the number of people having oral deficiency is expanding. It is proved that instrumental texture evaluation method that the authors developed is applicable to a wide range of food texture, particularly for viscoelastic gels, with some changes of instrumental operation condition if necessary, providing a simple method for assessing textural acceptability of food products for consumption without using human subjects. From an industrial point of view, this method can contribute to the texture design of food products that are comfortable to eat and thus to the improvement of quality of life for those people. From a scientific point of view, this method can contribute to better understanding of the physiology of human tongue‐palate compression as an oral strategy for size reduction, particularly during consumption of solid or semi‐solid foods.

Temporal changes in cerebral blood flow induced by jaw movement have yet to be investigated. To assess the influence of pattern and intensity of muscle contraction during jaw movement on task-induced change in cerebral blood flow, we performed bilateral transcranial Doppler ultrasound examination during clenching, gum chewing, and tooth tapping in healthy volunteers. A random-effects model analysis revealed a significant increase in middle cerebral artery blood flow velocity during clenching (high muscle activity) and gum chewing (moderate muscle activity), compared with the preceding rest period; however, such an increase was not detected during tooth tapping (low muscle activity). Cerebral blood flow was greater on the working side during the intensive isometric contraction of the masseter muscle in clenching. These results suggest that task-induced change in cerebral blood flow during jaw movement is influenced by the change in peripheral circulation evoked by muscle contraction.