A Precise and Portable Gustatory Stimulator

Gustatory stimulation during neuroscience experiments proves to be exceptionally challenging, as the required stimulus control is non-trivial. We designed a new stimulator that meets the demands of behavioral, EEG/MEG, and neuroimaging (fMRI) studies. The device is based on the ne MESYS syringe pump system (Cetoni, Korbußen/Germany) and controlled through a Python-based software package. The system is portable and modular and can be equipped with multiple pumps, valves, and digital I/O boards for sending triggers to any laboratory equipment. The pumps deliver stimuli through plastic tubing to commercially available or custom-made mouthpieces or spray heads. Another distinguishing feature is the system’s ability to stimulate either side of the tongue independently. We present latency measurements that highlight the precision and reliability over time using two spray heads placed side-by-side. The delay between triggering the pumps and onset of liquid delivery showed minuscule variation within and across pumps (SDs <2ms and <1ms, resp.). We validated a lateralized setup in a behavioral study using spray heads on either side of a plastic barrier spatially separating the tongue at the midline. 18 participants (p.; median age: 28.6y; 13f) performed two tasks. During the taste task, salty (2% NaCl) stimuli were presented on both or only one side of the tongue, while water was sprayed on the other, and p.s reported the locus of taste stimulation (left, right, both). In the touch task, water was sprayed on both or only one side of the tongue and p.s reported the locus of touch. P.s identified 69% of the taste and 91% of the touch stimulations correctly, corroborating that the liquids did not cross the barrier, and demonstrating the suitability of the stimulator for use in complex experimental setups

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