Abstract
Obese individuals discount future rewards to a higher degree than lean individuals, which is generally considered disadvantageous. Moreover, their decisions are altered more easily by decision-irrelevant cues. Here, we investigated neural correlates of this phenomenon using functional MRI. We tested 30 lean and 26 obese human subjects on a primed delay discounting paradigm using gustatory and visual cues of positive, neutral and negative valence to bias their intertemporal preferences. We hypothesised that activation differences in reward-related and behavioural control areas, and changes in connectivity between these areas, would reflect the effect of these cues. Here, obese subjects were more susceptible to priming with negative gustatory cues towards delayed choices as opposed to lean subjects. This was related to lower activity in the left dorsolateral prefrontal cortex during priming. Modulation of functional connectivity between the dlPFC and the ventromedial PFC by the behavioural priming effect correlated negatively with BMI. This might indicate that default goals of obese individuals were different from those of lean participants, as the dlPFC has been suggested to be involved in internal goal pursuit. The present results further our understanding of the role of the PFC in decision-making and might inform future weight-management approaches based on non-invasive brain stimulation.
Highlights
One of the features most consistently shown to be associated with obesity measures is temporal impulsivity[1,2], a subdomain of general impulsivity[3,4]
In this study we investigated whether 1) obese participants showed higher delay discounting than lean participants, and 2) whether they were more susceptible to incidental priming on the delay discounting paradigm than lean individuals
We showed higher baseline delay discounting for obese compared to lean individuals independent of delay
Summary
One of the features most consistently shown to be associated with obesity measures is temporal impulsivity[1,2], a subdomain of general impulsivity[3,4]. Research shows that DD behaviour is malleable and depends largely on the framing of the two monetary options, paying attention to the delay vs the reward, time frames in which the options are available, or even framing options with decimal numbers vs without them[15,25] It can be influenced by stress, mood, affective stimuli[25] or incidental cues26–28 – cues not associated with the decision-making process at hand. The reason for this was that it is unknown from the current literature to which extent environmental food cues, which are thought to only exert an effect on dietary decisions, might generalise to other modalities, such as financial ones Such an influence has been shown before for a variety of stimuli, ranging from brand logos to foods (e.g.26,30), and there is further evidence that the brain automatically extracts specific image features related to decision-making even when presented as an incidental, task-irrelevant background image (e.g.31,32). We tested whether food cues can be used to alter disadvantageous decision making processes in obesity
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