Anodal Galvanic Taste Stimulation to the Chin Enhances Salty Taste of NaCl Water Solution

Galvanic taste stimulation (GTS) is a non-invasive electrical stimulation of sensory nerves that induces, inhibits, and enhances taste sensation. It has been shown that the cathodal GTS taste enhancement effect occurs when only cathodal electrodes are attached in or near the mouth, while anodal GTS, whose anodal electrodes are attached in or near the mouth, induces an electrical taste sensation rather than taste enhancement. In the present study, we focused on the taste enhancement effect of anodal GTS, enhancing the salty taste produced by a sodium chloride (NaCl) aqueous solution during stimulation. In this study, GTS was applied to the chin rather than the inner mouth so as not to disturb natural eating and drinking behavior, according to a previous study. To demonstrate and quantitatively evaluate its enhancement effect, we conducted two psychophysical experiments in which subjects were asked to indicate the intensity of the saltiness perceived during electrical stimulation by adjusting the concentration of aqueous NaCl to achieve a solution of equivalent saltiness. We discovered that the perceived intensity increased as the current intensity applied to the chin increased. Moreover, the magnification ratios against the baseline exceeded 1 under all conditions of the NaCl aqueous solution. These results indicate that anodal GTS is effective in enhancing the salty taste of NaCl aqueous solutions.

A preliminary study on digital image performance to stimulate food taste experience

Users and food marketers alike would share images of food in the hopes that viewers would be able to capture the emotion/sensation presented by the food. This is a form of food digitization, shifting away from the mechanical aspect of taste stimulation to the use of digitized visuals. This paper aim to evaluate the performance of taste perception made by users by just looking at food image. Using food images as a medium of taste stimulation, this paper reports international users’ perception of the taste of Malaysian local food through an online channel. By applying SPSS analysis, the author studied the patterns of similarity and dissimilarity of users’ perception of food images that have been compiled using an online survey. Interestingly observed, the results of the analysis enable the author to assess how close user perceptions were akin to the real taste. The author found that most user perceptions are closely matched with the food’s real taste which allows the author to conclude that visual media is possible in stimulating food taste experience. It is good news for food marketers and food tourism. Nevertheless, more samples of food images are required to further attest these findings.

Hedonicity in functional motor disorders: a chemosensory study assessing taste

The aim of this study was to explore hedonicity to basic tastes in patients with functional motor disorders (FMDs) that are often associated with impairment in emotional processing. We recruited 20 FMD patients and 24 healthy subjects, matched for age and sex. Subjects were asked to rate the hedonic sensation (i.e., pleasant, neutral, and unpleasant) on a − 10 to +10 scale to the four basic tastes (sweet, sour, salty, and bitter) at different concentrations, and neutral stimuli (i.e., no taste stimulation) by means of the Taste Strips Test. Anxiety, depression, and alexithymia were assessed. FMD patients rated the highest concentration of sweet taste (6.7 ± 2.6) as significantly more pleasant than controls (4.7 ± 2.5, p = 0.03), and the neutral stimuli significantly more unpleasant (patients: − 0.7 ± 0.4, controls: 0.1 ± 0.4, p = 0.013). Hedonic ratings were not correlated to anxiety, depression, or alexithymia scores. Hedonic response to taste is altered in FMD patients. This preliminary finding might result from abnormal interaction between sensory processing and emotional valence.

Searching for relief: Drosophila melanogaster navigation in a virtual bitter maze

Animals use pain-relief learning to discern which actions can diminish or abolish noxious stimuli. If relief from pain is provided in a specific location, place learning is the mechanism used to pinpoint that location in space. Little is known about how physiological and non-directly damaging stimuli can alter visual-based searching behaviour in animals. Here we show how the optogenetically-induced activation of bitter-sensing neurons urges Drosophila melanogaster to seek relief from bitter taste stimulation and that this distressful, but ecologically relevant stimulus, innately wired to the threat of intoxication, is sufficient to elicit pain-relief-like behavioural responses. Specifically, freely walking flies inside an open circular arena are trained to seek relief from the unpleasant stimulation by searching for a safe area alternatively positioned in the proximity of a pair of identical, diametrically opposed, visual markers. Moreover, and perhaps more importantly, under this paradigm flies develop visual place learning manifested by their seeking relief in the zone associated with bitter relief during the last trial of training, even when exposed to constant bitter stimulation with no relief provided. An important implication is that this form of learning does not lead to operant conditioning generalization. We further propose that kinematic indexes, such as the spatially-specific reduction of locomotor velocity, may provide immediate evidence of relief-based place learning and spatial memory.