Development of a Stimulation System for the Gustatory Eye-Blink Response in Humans

An inexpensive stimulation system for recording eye-blink responses elicited by taste stimuli has been developed using a manually controlled syringe and tasimetric sensor. The system requires neither an intra-oral device nor clamping of the head and tongue for natural eye-blink responses. The data recorded by the system have a high temporal resolution that is likely to be sufficient for the analysis of eye-blink responses based on video recordings.

Influence of Sex Differences on Temporal Sequence of Sensations after Ingesting Fruit-Flavored Tea—A Preliminary Study

The goal of this preliminary study was to examine the effect of participants’ sexes on the temporal sequence of dominant sensations elicited by fruit-flavored teas. Twelve healthy young adults were assigned to male (n = 6) and female (n = 6) groups. Both groups were evaluated for four sensations using four fruit-flavored teas with 0.05 M sucrose using the temporal dominance of sensations (TDS) method. Only two sensations, sweetness and fruitiness, were consistently reported in the two groups. The male group first reported fruitiness and then sweetness as the dominant sensation following ingestion of the samples. Conversely, the female group reported these two dominant sensations in the reverse order. Significant dominant durations between the two sensations largely varied among the samples in both groups. These results suggest that there are sex-based differences in the temporal sequence of dominant sensations elicited by fruit-flavored teas as evaluated by the TDS method.

Classification of Masseter Activity Patterns during Chewing in Healthy Young Adults: The Effect of Taste Signals

This study examined the effects of the textural properties and chemical components of foods on masseter activity patterns. Ten healthy young participants (seven men and three women) were asked to chew four gummy candies with different flavors while their masseter activities were recorded by a surface electromyogram. The masseter activity patterns during chewing were analyzed quantitatively using a TP technique, generating three TP values (T25, T50 and T75). The textural analysis included four representative properties, and six sugars and four organic acids were tested in the chemical analysis. The hierarchical cluster analysis classified the T25 and T75 values into four subclusters and classified the T50 values into three subclusters. Two T75 subclusters differed significantly in the combined amounts of the two predominant sugars (sucrose and maltose);however, these T75 subclusters did not differ in their organic acid contents or textural properties. Therefore, sucrose and maltose affect masseter activity patterns during chewing, particularly in the later stage of masseter activity.

Quantitative Analysis of Relationships between Masseter Activity during Chewing and Textural Properties of Foods

The aim of this study was to quantify the relationships between four physiological parameters of masseter activity during chewing and properties related to the sizes and textures of the six representative test foods. The physiological parameters analyzed were the number of chewing cycles, chewing time, masseter amplitude, and cycle duration, which were obtained from masseter surface electromyography recorded in ten (seven male and three female) healthy, young participants. The six test foods differed in size dimensions (length, width, and height) and in textural properties (hardness, fracturability, and adhesiveness). The quantitative relationships were examined using linear regression. Nine statistically significant regression coefficients were found between the four physiological parameters and the textural properties, but not the height, of the test foods. From the regression coefficients, contributions of the food properties to the physiological parameters were estimated. Individual relationships between the physiological parameters and textural properties of the test foods are discussed in relation to their physiological implications.

The Effect of Masseter Activity Patterns during Chewing on Suprahyoid Activity in Subsequent Chewing Cycles

Few studies have evaluated the effects of activity patterns of the jaw closing muscles assessed by specific parameters on jaw opening in subsequent cycles during the chewing of food. The objective of this study was to quantitatively analyze the effect of the masseter (jaw closer) activity patterns on suprahyoid (jaw opener) activity during subsequent cycles. The assessments were performed while participants naturally chewed six test foods that differed in size dimensions and textural properties. Surface electromyograms of the masseter (on the habitual working side) and suprahyoid muscles were recorded in ten healthy young adults, each of whom randomly received one of the six test foods. The activity patterns were assessed using three parameters specifically developed for their quantification. Changes in suprahyoid activity during each of the subsequent chewing cycles were examined by three amplitudinal (minimum, maximum, and net values of the integrated suprahyoid electromyogram) parameters and one durational (active duration) parameter. The main finding was that two of the three activity pattern parameters had a statistically significant effect only on the three amplitudinal parameters in three of the six test foods. These results suggest that masseter activity patterns partially affect suprahyoid activity during subsequent chewing cycles and that the effect is food dependent. A possible neural mechanism responsible for this effect is presented.

Eye Blink Responses to the Four Basic Taste Stimuli in Healthy Young Humans

Taste stimuli can elicit facial responses, and the facial responses may be useful indexes of taste sensations. In this study, we propose that eye blinking is also elicited by taste stimuli and we examined eye blink responses in six healthy young adults. Low and high concentration solutions of the four basic taste qualities (sweetness, saltiness, sourness, and bitterness) and distilled water were delivered via a silicone tube. Facial responses were recorded by a video camera and eye blink responses were identified. The number of eye blinks in the 5 s following stimulation, and the latency and duration of the first eye blink, were quantified. High concentrations of sour and bitter solutions increased the number of eye blinks (195% and 227%, respectively;P P

A Piezoelectric Sensor-Based System for Objective Analyzing of the Preparation of Fluid Foods

A monitoring system using a piezoelectric sensor was developed for the quantitative analysis of the stirring process in which a mixture of a thickener with water was prepared. A thin piezoelectric sensor film was attached to the inside of a glass container in which the mixture was stirred and connected to a recorder. Seven healthy young participants were asked to conduct stirring for 90 s at three cycles per second (3 Hz). A triphasic wave with a large upward peak was recorded in each cycle of stirring. The average period across the seven participants was 0.337 s (n = 613 cycles), and statistical analysis revealed no significant difference between the average value and the expected value of 0.333 s. Video images captured during stirring were analyzed, and the analysis showed that the peak of the large upward wave appeared approximately 0.12 s (approximately 36% of the average period) after the time when the spoon head for stirring passed near the piezoelectric sensor. The monitoring system developed in this study allows the precise temporal analysis of stirring for the preparation of a mixture.