In this study, we aimed to investigate whether flavour perception can be modulated by non-invasive brain stimulation (NIBS) using transcranial direct current stimulation (tDCS) targeting the intraparietal sulcus (IPS), a multisensory integration area implicated in flavour perception. We chose specialty coffee as our stimulus due to its complexity and diverse flavour profiles, as well as, established industry standard rating procedures. Our hypothesis stated that stimulation of the IPS with cathodal tDCS would modulate coffee flavour perception on at least one of its characteristics, such as acidity, sweetness, or aftertaste.

We conducted a sensory evaluation training followed by a sensory evaluation task on a separate day in which participants tasted coffee samples and rated their flavour characteristics under two conditions: with and without tDCS brain stimulation over bilateral IPS. We found that stimulation with cathodal tDCS modulated hedonic judgments of flavour characteristics, specifically body level and overall rating. Moreover, we observed less consistency in ratings under the stimulation condition compared to the non-stimulation condition, as well as compared to consistency among expert coffee raters.

Our findings provide proof of principle that non-invasive brain stimulation with tDCS can modulate flavour perception in humans, supporting the notion that the IPS plays a role in integrating information from different sensory modalities to create a cohesive perceptual experience of flavour. This study contributes to the growing body of research on the influence of brain stimulation techniques on cognitive processing and sheds light on the potential of tDCS as a tool for investigating the neural mechanisms underlying flavour perception. Further research with larger sample sizes and more complex designs is warranted to better understand the underlying mechanisms and potential applications of brain stimulation in modulating flavour perception.