Differential neural correlates of oral capsaicin pleasantness in habitual and non-habitual spicy eaters

Repeated exposure to spicy flavor can shift individuals' preferences for capsaicin-containing stimuli, however, the neural mechanisms underlying the hedonic processing of oral capsaicin remain unclear. Here, we investigated how habitual spicy food consumption modulates brain responses involved in hedonic perceptions of oral capsaicin. Using functional magnetic resonance imaging, we compared brain activity between high-frequency (HF, N = 19) and low-frequency (LF, N = 17) spicy food consumers during oral administration of three concentrations of capsaicin (10, 30, 60 μM) and water as a control stimulus. Participants rated the pleasantness and intensity after each stimulus. Compared with the LF group, the HF group reported significantly higher pleasantness ratings across all capsaicin concentrations, an effect that was independent of perceived intensity. At the neural level, a significant group × concentration interaction was observed. For the high-concentration of capsaicin stimulation (60 μM), the HF group exhibited increased activation in the left postcentral gyrus and decreased activation in the right hippocampus relative to the LF group. In the LF group, pleasantness for the high concentration of capsaicin was positively correlated with activation in the right hippocampus. For the low-concentration of capsaicin (10 μM), the LF group showed weakened hippocampus-postcentral and hippocampus-caudate connectivity, but stronger insula-parahippocampal connectivity compared to the HF group. In addition, pleasantness ratings for low-concentration of capsaicin were positively correlated with hippocampus-postcentral connectivity in LF participants. Together, these findings suggest that the neural substrates subserving the hedonic processing of oral capsaicin vary as a function of habitual spicy food intake and stimulus concentration, reflecting experience-dependent plasticity within chemosensory and affective brain networks.