title: Fuel not fun: Reinterpreting attenuated brain responses to reward in obesity.
abstract: There is a well-established literature linking obesity to altered dopamine signaling and brain response to food-related stimuli. Neuroimaging studies frequently report enhanced responses in dopaminergic regions during food anticipation and decreased responses during reward receipt. This has been interpreted as reflecting anticipatory "reward surfeit", and consummatory "reward deficiency". In particular, attenuated response in the dorsal striatum to primary food rewards is proposed to reflect anhedonia, which leads to overeating in an attempt to compensate for the reward deficit. In this paper, we propose an alternative view. We consider brain response to food-related stimuli in a reinforcement-learning framework, which can be employed to separate the contributions of reward sensitivity and reward-related learning that are typically entangled in the brain response to reward. Consequently, we posit that decreased striatal responses to milkshake receipt reflect reduced reward-related learning rather than reward deficiency or anhedonia because reduced reward sensitivity would translate uniformly into reduced anticipatory and consummatory responses to reward. By re-conceptualizing reward deficiency as a shift in learning about subjective value of rewards, we attempt to reconcile neuroimaging findings with the putative role of dopamine in effort, energy expenditure and exploration and suggest that attenuated brain responses to energy dense foods reflect the "fuel", not the fun entailed by the reward.
authors.affiliation: Department of Psychiatry and Neuroimaging Center, Technische Universität Dresden, 01187 Dresden, Germany; The John B. Pierce Laboratory, New Haven, CT 06519, USA; Department of Psychiatry, Yale University, New Haven, CT, 06519, USA. Electronic address: nils.kroemer@tu-dresden.de.
authors.forename: Nils B
authors.initials: NB
authors.lastname: Kroemer
authors.affiliation: The John B. Pierce Laboratory, New Haven, CT 06519, USA; Department of Psychiatry, Yale University, New Haven, CT, 06519, USA; Yale Interdepartmental Neuroscience Program, Yale University, New Haven, CT 06520, USA; Department of Psychology, Yale University, New Haven, CT 06520, USA.
authors.forename: Dana M
authors.initials: DM
authors.lastname: Small
mesh_terms: D000818:Animals; D059031:Anticipation, Psychological / Q000502:physiology*; D001931:Brain Mapping; D003342:Corpus Striatum / Q000000981:diagnostic imaging / Q000503:physiopathology*; D005502:Food; D006801:Humans; D059906:Neuroimaging; D009765:Obesity / Q000000981:diagnostic imaging / Q000473:pathology* / Q000523:psychology; D012054:Reinforcement, Psychology
keywords: Anhedonia; Dorsal striatum; Food reward; Reinforcement learning; Reward deficiency; fMRI