The Neural and Perceptual Effects of Stevia During Retronasal Occlusion

We have recently shown that occluding retronasal pathways with a nose clip reduces both the subjective and neural responses to sucrose, suggesting the involvement of retronasal pathways in sucrose perception. However, how other sweet tastes such as stevia might also be affected by retronasal occlusion at the subjective and neural level is unknown. We examined the neural activity to stevia with a nose clip on (blocking retronasal pathways) and nose clip off, in a robust sample of healthy adults (N = 34, mean 25 years). Neural activity to stevia was reduced with the nose clip on in the olfactory cortex, hypothalamus, the subgenual and pregenual anterior cingulate and the nucleus accumbens. Stevia pleasantness was tracked by the posterior insula, but this was not apparent with the nose clip on. In conclusion, our findings are the first to demonstrate that blocking retronasal pathways significantly reduces neural responses to stevia taste, supporting the proposal that retronasal pathways play a role in the perception of tastes like stevia, and that stevia-sweetened products could be made more palatable via retronasal pathways.