Potential consequences of adverse lifestyle factors on decision-making as modeled by the Drosophila melanogaster egg-laying process

Studies have shown that lifestyle factors including impaired gut microbiome health, advanced maternal age, and a diet high in sugar may negatively impact cognitive functioning, but their effects on decision-making have not been thoroughly examined. This study aimed to describe the effects of these three factors on decision-making as well as to determine whether the mechanism behind these effects is metabolic or sensory. This was assessed using Drosophila melanogaster egg-laying chamber assays in which Drosophila were given two choices of substrate on which to lay their eggs: sucrose vs. plain or sucrose vs. sucrose. It was found that neither a reduced gut microbiome nor advanced maternal age influenced decision-making. A high-sugar diet resulted in increased sucrose preference. Neither a metabolic nor a peripheral sensory mechanism explained this phenotype, for ingesting just the nutritious element of sucrose nor just peripheral sensing of the sweet element of sucrose was sufficient to increase sucrose preference. An internal sensory mechanism using Gr43A neurons partially accounted for this phenotype, for the lack of internal sensor activity prevented the unfavorable assessment of sweetness, increasing the perceived value of sucrose. It can be concluded that a diet surpassing healthy sugar levels caused adverse changes in decision-making through a combination of metabolic and sensory mechanisms. This study fills the gap in research about whether lifestyle factors affect decision-making in humans and in Drosophila. The results of this study can be a motivator for people to adopt healthier diets and monitor their sugar intake.