A new gustometer: Template for the construction of a portable and modular stimulator for taste and lingual touch

Taste research has been hampered by technical difficulties, mostly because liquid taste stimuli are difficult to control in terms of timing and application area. Exact stimulus control requires a gustometer, but the existing devices are either not well-documented or rather inflexible. We designed a gustometer based on a computer-controlled, modular pump system, which can be extended via additional hardware modules-for example, for heating of the stimuli or sending and receiving triggers. All components are available for purchase "off the shelf." The pumps deliver liquids through plastic tubing and can be connected to commercially available or custom-made mouthpieces. We determined the temporal precision of the device. Onset delays showed minuscule variation within pumps (SD < 3 ms) and small differences between pumps (< 4.5 ms). The rise time was less than 2 ms (SD < 2 ms), and the dosage volume bias was only 2%. To test whether hemitongues could be stimulated independently, we conducted a behavioral experiment. A total of 18 participants received tasteless stimuli to the left, right, or both sides of the tongue. The side of stimulation was correctly identified on 91% of trials, indicating that the setup is suitable for lateralized stimulation. Electroencephalographic responses to water and salty stimuli were recorded from two participants; the stimulation successfully evoked event-related responses, demonstrating the suitability of the device for use in electrophysiological investigations. We provide a Python-based open-source software package and a Web interface to easily operate the system. We thereby hope to facilitate access to state-of-the-art taste research methods and to increase reproducibility across laboratories.