Anodal galvanic taste stimulation to the chin enhances salty taste of NaCl water solution

Abstract

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.