@[toc](Contents) ## Project Summary The neurotransmitter dopamine plays a central role in several cognitive domains such as motivation, reward-processing, reinforcement learning, decision-making and executive functions including working memory and attention (Arnsten, Wang, & Paspalas, 2012; Logue & Gould, 2013; Rogers, 2011; Schultz, 2002; Volkow, Wise, & Baler, 2017). Results of our recent studies point towards prominent alterations in these domains in overweight and obesity and suggest the existence of a non-linear relationship between markers of obesity and central dopamine tone (Horstmann, Fenske, & Hankir, 2015). Dopamine tone in the brain depends on both genetic and environmental factors. Genetic differences in important genes within the dopaminergic synapse, i.e. COMT (important for dopamine degradation) and dopamine receptor D2 (A1 allele of Taq1A), lead to altered dopamine signaling and can therefore contribute to higher vulnerability for diet-induced obesity (Annerbrink et al., 2008; Epstein et al., 2007). One important environmental factor that is hypothesized to affect dopamine transmission in obesity is an unhealthy diet. Accumulating evidence from animal research suggests that observed differences in dopamine signaling in obesity may be induced by diet rather than obesity (Geiger et al., 2009; Narayanaswami, Thompson, Cassis, Bardo, & Dwoskin, 2013; van de Giessen et al., 2013; Vucetic, Carlin, Totoki, & Reyes, 2012). However, the evidence for diet-induced alterations in dopamine signal transmission and their effects on dopamine-mediated cognitive processes in humans is scarce. In the proposed study, we aim to address the effect of diet high in fat and sugar on dopamine signal transmission in the brain and on dopamine-mediated cognitive performance. ## Preregistrations The available preregistrations belonging to the study are listed under "Registrations": ### Current - up to date **umbrella preregistration** (with analysis plan and updated sample size): - The interplay between dopamine genes and diet, 2020-03-24, https://osf.io/w9e5y. - preregistration of the **epigenetics sub-project**: - The interplay between dopamine genes and diet, 2019-09-24, https://osf.io/e3w8k. - preregistration of the **working memory sub-project**: - The association of high saturated fat and added sugar consumption with the ability to update and ignore working memory content, 2020-07-17, https://osf.io/8gtfk. - detailed **material and methods** for the complete study - see attached pdf file "The interplay between dopamine genes and diet - detailed material and methods" ### Previous version - the original **umbrella preregistration** (without analysis plan): - The interplay between dopamine genes and diet, 2019-02-18, https://osf.io/8pxgd. All preregistrations have been published during or after data collection, and before analyzing the dataset of interest. This is specified in the respective preregistrations. ## Contact Should you have any questions regarding the study in general or any of its sub-projects, please contact our lab coordinator via https://obrainlab.com/contact/