Enhancement of orbitofrontal and insular cortices responses to spicy perception increases high salt sensation: An event-related potentials study

Context: The interplay between taste perception and salt sensation is crucial for salt intake. Our hemodynamic neuroimaging research has shown that the administration of capsaicin (the major spicy component of chili peppers) enhances the metabolic activity of the insula and orbitofrontal cortex (OFC) in response to high salt intake. Aims: The aim is to study how the brain processes underlying salty taste and spicy perception within the first second after stimulation. Settings and Design: This electrophysiological study included 25 participants (10 males) who were recruited by advertisement flyers in Chongqing. Subjects and Methods: The present study investigated the responses of the OFC and insular to the interaction of spicy flavor and salty taste by recording the event-related potentials (ERPs). Two concentrations of sodium chloride solution (150 and 200 mmol/L) with or without 0.5 μM capsaicin were applied to the tongue of the study's participants. Statistical Analysis Used: One-way ANOVA with Games-Howell's multiple comparison post-hoc tests and linear regression analysis. Results: N1 amplitudes were positively correlated with participants' levels of salt intake and their salty preference scores. Source analysis performed on the ERP N1 wave in the 120–180 ms time window showed that the sources were located approximately in the insula and OFC. The amplitudes of the N1 and P2 components in the 200 mmol/L NaCl group were higher than those in 150 mmol/L NaCl group, but not significantly different than the group administered 150 mmol/L of NaCl and 0.5 μmol/L of capsaicin. Conclusions: The present study provides novel insights into the use of flavor or saltiness enhancers for salt reduction in humans through cortical responses to the spicy-salty interaction.