The primary purpose of this study was to determine whether body posture altered the duration of oral swallowing. To answer this question, we recorded electromyograms (EMGs) from the anterior tongue and suprahyoid (SH) muscles as well as laryngeal movement associated with swallowing in nine normal young subjects. The subjects swallowed a test food after receiving a signal while in four randomly set postures: upright, two inclined (60 degrees and 30 degrees to the horizontal), and supine positions. We measured the durations from the start to the peak and from the peak to the end of the integrated tongue and SH EMGs. We assumed that the duration from the start to the peak of the integrated SH EMG would correspond to the duration of oral swallowing. The average duration from the start to the peak of the integrated SH EMG decreased after moving from the upright to the inclined and supine positions. The decrease in the duration was statistically significant and consistent for three experimental sessions. The duration from the start to the peak of the integrated tongue EMG during swallowing tended to decrease after lying down, but not significantly. The postural changes did not affect the remaining four durations. The decrease in the duration of oral swallowing induced by lying down suggests that the gravitational force placed on the test food facilitates the swallowing reflex. Large variation in the tongue activity during swallowing among the subjects can probably be attributed to the lack of a significant decrease in the duration of the tongue activity.

This study examined the influences of rheological properties on mastication in eight healthy male subjects by recording an electromyogram (EMG) of the masseter (MS) muscle during chewing. Four different agars were tested: 0.5 and 1.5% ordinary agars (0.5OA and 1.5OA), and 2.5 and 4.0% . The hardness, adhesiveness and cohesiveness differed among the four agars, which is most likely because of the differences in the concentrations and constituents of the agars. Mastication time and the average amplitude of the MS EMG during chewing were longest and largest, respectively, with the 1.5OA followed by the 4.0IA. The activity pattern of the MS EMG differed between the first and last cycles of chewing sequences in each of the agars used; there were no differences between the first cycle activity patterns or the last cycle activity patterns when comparisons were made between the four agars. These results suggest that the rheological properties of the agars modify mastication and that the activity patterns of the MS muscle change during chewing. PRACTICAL APPLICATIONSThe present findings obtained by the analyses of rheological properties and physiological parameters, especially by the "T P " technique, suggest the following possible uses: (1) the T P technique can analyze foods at different angles from analysis by rheological properties; (2) a combination of rheologi-1

Activity patterns of the suprahyoid muscles were examined using a new analytical technique. The suprahyoid activities were recorded during swallowing of tasteless foods and foods with taste qualities (sweet, salty, sour, bitter and umami). The technique involved: (1) division of cumulative integrated suprahyoid activities from each swallow into 10 equal sections and (2) assignment of individually sectioned activities to a standardized timescale as T P (from T 10 to T 100 ; relative time for P% of the cumulative electromyogram) to enable comparison of data from different trials. Three significant differences were found in T p between the following foods: tasteless and sour, tasteless and bitter, and sour and umami. However, the differences were not repeatedly confirmed. These results suggest that gustatory signals from food tastes affect differentially the activity patterns of the suprahyoid muscles during pharyngeal swallowing, although the effect is not permanent. This method may be used to measure taste impressions in infants and in certain disabled subjects. 3 Corresponding author. TEL and FAX: +81-25-257-4477; EMAIL: miyaoka@nuhw.ac.jp Journal of Sensory Studies 20 (2005) 473-483. All Rights Reserved.

The purpose of this study was to determine (i) whether or not textural properties of foods and body positions affect the durations of anterior tongue and suprahyoid muscle activities during swallowing, and (ii) if such changes occur, is the 'pre-peak' or the 'post-peak' duration of integrated muscle activity responsible. We used two test foods with different properties of hardness and adhesiveness. We recorded electromyograms (EMGs) from the anterior tongue and suprahyoid muscles as well as the laryngeal movement associated with swallowing in normal subjects (six men and three women; 21-30-years old). The subjects swallowed the test foods in four randomly set postures: upright, two inclined (60 degrees and 30 degrees to horizontal), and supine. None of the measured durations for the anterior tongue and suprahyoid EMGs were different among the four positions during swallowing of either food. The 'total' duration, from the start to the end of the integrated EMG, of anterior tongue activity was significantly (P<0.001, anova) longer during the swallowing of the tougher and more adhesive food than during swallowing of the other food, but the 'total' duration of suprahyoid activity was unchanged. The 'post-peak' duration of anterior tongue activity, which stretched from the peak to the end of the integrated EMG, was also significantly longer (P<0.001, anova) during swallowing of the tougher and more adhesive food. The results indicate that tougher and more adhesive foods prolong the duration, especially the 'post-peak' duration, of anterior tongue activity during swallowing in the upright, inclined and supine positions.

This study was designed to examine the effect of different food properties and body positions on electromyographic amplitudes of the anterior tongue (AT) and suprahyoid (SH) muscles during swallowing in normal subjects (six men and three women; 21-30 years old). Each subject was asked to swallow three foods (consisting of 2.0%, 5.7% or 9.1% of a thickening agent dissolved in water) with different textural properties in one of four body positions: upright, inclined at 60 degrees or 30 degrees , or supine. Surface electromyograms (EMG) were recorded from the anterior tongue and SH muscles, and the integrated and cumulated EMG were used to evaluate the amplitude changes. The increases in food hardness and adhesiveness elevated the integrated and cumulated EMGs of both the AT and SH muscles during swallowing in a stepwise manner (P < 0.0001, one-way anova) that was independent of the body position. There was a linear relationship between the concentrations of the thickening agent and the logarithmic values of the food hardness. There was also a parallel relationship between the logarithmic hardness values and the final logarithmic values of the cumulated muscle activity during swallowing. Unlike these simple amplitude responses of the AT and SH muscles to the different food properties, our previous studies have shown that the durational responses of these muscle activities to different food properties are more complicated. Possible neural mechanisms responsible for the amplitude responses observed are discussed.