Prefrontal hemodynamic responses to astringency aftertaste across alcoholic and alcohol-free matrices: A functional near-infrared spectroscopy study.

Astringency is an important mouthfeel attribute in many beverages, yet its neurophysiological correlates remain poorly understood. It also remains unclear how beverage matrix shapes frontal hemodynamic responses to astringency over time. This study used functional near-infrared spectroscopy (fNIRS) to characterize prefrontal hemodynamic responses to proanthocyanidin (PAC)-induced astringency in three matrices: water, ethanol, and red wine. To capture temporal aspects of the perceptual experience, responses were assessed separately during the induction and aftertaste phases. Sensory evaluation showed that perceived astringency increased with PAC concentration, although both the magnitude and time course of this increase varied across matrices. During the induction phase, frontal HbO responses were generally limited and less consistent. By contrast, the aftertaste phase was associated with broader and stronger prefrontal HbO responses. Region-of-interest analysis further revealed distinct matrix-related response patterns in channels corresponding anatomically to the orbitofrontal cortex (OFC), frontopolar area (FPA), and dorsolateral prefrontal cortex (DLPFC), suggesting that lingering astringency may involve distributed evaluative processing rather than a simple representation of perceived intensity. Overall, prefrontal HbO responses to astringency differed between the induction and aftertaste phases and varied across beverage matrices. This work extends current understanding of astringency as a matrix-sensitive sensory process and provides useful neurophysiological evidence concerning the frontal hemodynamic correlates of persistent mouthfeel attributes in food systems.