Hajime Iwamori

Analysis of the pattern of suprahyoid muscle activity during pharyngeal swallowing of foods by healthy young subjects

We previously developed the TP technique to discriminate between the activity patterns of skeletal muscles. In this study we aim to identify the TP value(s) that can be used to sensitively evaluate the activity patterns of the suprahyoid (SH) muscles during swallowing. We also analyse the effect of food textural properties on the activity patterns of the SH muscle during oral and pharyngeal swallowing. Three test foods consisting of 3%, 6% and 9% of a thickening agent, Mousse-up (MU) were prepared. Their textural properties differed significantly. Swallowing of 9% MU involved a significantly longer average duration than 3% MU. The average T50 value for 6% MU was significantly larger than that for 3% MU. However, the average T20 and T80 values of the test foods did not differ. Thus, the T50 value is particularly suitable for evaluating SH muscle swallowing patterns. Moreover, test foods that vary in their textural properties elicit different durations and patterns of SH muscle activity.

Sequential analysis of masseter activity patterns during chewing in healthy males

Abstract The present study examined sequential changes in masseter activity patterns observed during chewing of four different agar samples in eight healthy young males. Two parameters, T50 and D50, were specifically used for evaluation of the activity patterns of individual bursts. Statistical significances were detected in regression coefficients (21.9% of 32 trials) and Spearman’s rank correlation coefficients (28.1%) between the calculated T50 values and chewing cycles, whereas no significant differences among the four agar samples were found. Three (I–III) types of activity patterns of masseter bursts during chewing sequences were classified by the D50 values, which were derived from the T50 values. The three types physiologically corresponded to incrementing (Type I), decrementing (Type III) and mixed discharge patterns (Type II). The classification of activity patterns suggested the usefulness of D50 values in the sequential analysis of masseter activity patterns.

Synchronization of masseter activity patterns between the right and left sides during chewing in healthy young males

Abstract Masseter activity patterns during chewing, which were quantitatively assessed using T50 values, were compared between the right and left sides of healthy young males. Surface electromyograms were recorded from both masseters, and each participant was asked to chew four different agar samples at his own pace across two separate sessions. The four agar samples, each possessing differing textural properties, consisted of two normal and two distinctive agar varieties. The Pearson’s correlation coefficient was calculated for each pair of T50 values to evaluate the degree of synchronization of activity patterns between both masseters. A three-way analysis of variance revealed significant main effects of the ‘participant’ and ‘experimental session’ factors, but not of the ‘test food’. The number of significant coefficients increased stepwise by increasing the number of chews per sequence. These results suggest the importance of the initial stages of chewing sequences in facilitating the synchronization of bilateral masseter activity patterns.

Distribution of Recognition Times to Fruity Flavor of Gummy Candies in Healthy Adults

Times for recognition of fruity flavors in six gummy candies were measured using an electromyography-based system in 23 young healthy participants. They were instructed to chew one of the gummy candies at a random order and to press a button as soon as possible when they recognized what flavor was. The measured 181 recognition times showed two distributions, normally (n = 107) and non-normally (n = 74). The overall average of the normal distribution was 7.5 seconds (±2.34 seconds; standard deviation), and there were no differences in the average ratios among the gummy candies. Eighteen of the participants reported 41 inconsistent reports with flavors that were provided by the manufacturer. The most frequently observed report was an apple-flavored gummy candy (14, 34.1%) mainly for a pear-flavored. However, there was no significant correlation between the numbers of recognition times and those of inconsistent flavors among the used gummy candies.