The effect of cognitive load on preference and intensity processing of sweet taste in the brain

Distracted eating can cause overconsumption. Whereas previous work has shown that cognitive load leads to lower subjective taste intensity and increased subsequent consumption, the mechanism behind distraction-induced overconsumption remains unclear. To elucidate this, we performed two event-related fMRI experiments that examined how cognitive load affects neural responses and subjective ratings in terms of intensity and preference, respectively, to solutions varying in intensity. In Experiment 1 (N=24), participants tasted weak sweet and strong sweet glucose solutions and rated their intensity while we concurrently varied cognitive load using a digit-span task. In Experiment 2 (N=22), participants tasted five different glucose concentrations under varying cognitive load and then indicated their preferences for these concentrations. Participants in Experiment 1 rated strong sweet solutions as less sweet under high compared to low cognitive load, which was accompanied by attenuated activation under high cognitive load in the right middle insula and bilateral DLPFC while tasting the strong vs. weak sweet solutions. Psychophysiological interaction analyses showed that cognitive load also altered connectivity between middle insula and nucleus accumbens and DLPFC and middle insula for the strong sweet solution. In Experiment 2, cognitive load did not affect participants’ preferences for the varying concentrations. fMRI results revealed that cognitive load attenuated DLPFC activation for the strongest sweet solutions in the study.In conclusion, our behavioral and neuroimaging results suggest that cognitive load dampens the sensory and preference processing of strong sweet solutions in particular, which may indicate higher competition for attentional resources for strong sweet than weak sweet solutions under high cognitive load. Implications for future research are discussed.