Multi-tasking with electronic devices, such as our smart phones or computers, has become common behavior in everyday life, and increasingly occurs during consumption of food. Such “distracted eating” has been shown to cause overeating, is associated with increased BMI, and with increased choices of palatable foods. However, it is unclear how distraction increases food intake.
Duif, I., Wegman, J., de Graaf, C., Smeets, PAM. & Aarts, E. (2020). Distraction decreases rIFG-putamen connectivity during goal-directed effort for food rewards. Scientific Reports volume 10, Article number: 19072
The hypotheses
To study the effect of distraction on effort for valued and devalued food reward, the study used a food-related outcome devaluation paradigm, and manipulated distraction using a categorical visual detection task of varying attentional load. It was hypothesised that distraction would disrupt goal-directed control for food reward in terms of button presses (primary objective), by acting on the vmPFC (primary objective) or other fronto-striatal regions (secondary objective), and by affecting functional connectivity with the vmPFC or other fronto-striatal regions resulting from these previous analyses (secondary objective) (see preregistration).
The study
Thirty-eight healthy normal-weight participants (28F; 10M) performed a visual detection task varying in attentional load (high vs. low distraction) during fMRI. Simultaneously, they exerted effort for sweet and savory food rewards by repeated button presses. Two fMRI runs were separated by sensory-specific satiation (outcome devaluation) of one of the (sweet or savory) reward outcomes, to assess outcome-sensitive, goal-directed, responses (valued vs. devalued reward, post vs. pre satiation).
The results
The primary hypothesis that more distraction leads to less activation in ventromedial prefrontal cortex (vmPFC) during goal-directed effort could not be verified. Behaviorally, distraction also did not affect effort for food reward following satiation across subjects. For the secondary hypothesis, it was assessed whether distraction affected other fronto-striatal regions during goal-directed effort. No such effects at our whole-brain corrected threshold were detected, but at an exploratory uncorrected threshold (p < 0.001), distraction decreased goal-directed responses (devalued vs. valued) in the right inferior frontal gyrus (rIFG). Analysis continued with this rIFG region for the next secondary hypothesis; specifically, that distraction would reduce functional connectivity with the fronto-striatal regions found in the previous analyses. Indeed, distraction decreased functional connectivity between the rIFG and left putamen for valued versus devalued food rewards (pFWE(cluster) < 0.05). In an exploratory brain-behavior analysis, it was found that distraction-sensitive rIFG-responses correlated negatively (r = − 0.40; p = 0.014) with the effect of distraction on effort. Specifically, decreased distraction-related rIFG-responses were associated with increased effort for food reward after satiation.
The conclusions
The paper discusses the absence of distraction effects on goal-directed responses in vmPFC and in behavior across participants. Based on the significant functional connectivity and brain-behavior results, it is suggested that distraction might attenuate the ability to inhibit responses for food reward after satiation by affecting the rIFG and its connection to the putamen.