title: Mesolimbic dopamine signals the value of work.
abstract: Dopamine cell firing can encode errors in reward prediction, providing a learning signal to guide future behavior. Yet dopamine is also a key modulator of motivation, invigorating current behavior. Existing theories propose that fast (phasic) dopamine fluctuations support learning, whereas much slower (tonic) dopamine changes are involved in motivation. We examined dopamine release in the nucleus accumbens across multiple time scales, using complementary microdialysis and voltammetric methods during adaptive decision-making. We found that minute-by-minute dopamine levels covaried with reward rate and motivational vigor. Second-by-second dopamine release encoded an estimate of temporally discounted future reward (a value function). Changing dopamine immediately altered willingness to work and reinforced preceding action choices by encoding temporal-difference reward prediction errors. Our results indicate that dopamine conveys a single, rapidly evolving decision variable, the available reward for investment of effort, which is employed for both learning and motivational functions.
authors.affiliation: Department of Psychology, University of Michigan, Ann Arbor, Michigan, USA.|Neuroscience Graduate Program, University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: Arif A
authors.identifier: http://orcid.org/0000-0001-7403-0067
authors.initials: AA
authors.lastname: Hamid
authors.affiliation: Department of Psychology, University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Pettibone
authors.affiliation: Department of Chemistry, University of Michigan, Ann Arbor, Michigan, USA.|Department of Pharmacology, University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: Omar S
authors.initials: OS
authors.lastname: Mabrouk
authors.affiliation: Department of Psychology, University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: Vaughn L
authors.initials: VL
authors.lastname: Hetrick
authors.affiliation: Department of Psychology, University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Schmidt
authors.affiliation: Department of Psychology, University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: Caitlin M
authors.initials: CM
authors.lastname: Vander Weele
authors.affiliation: Department of Chemistry, University of Michigan, Ann Arbor, Michigan, USA.|Department of Pharmacology, University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: Robert T
authors.initials: RT
authors.lastname: Kennedy
authors.affiliation: Department of Psychology, University of Michigan, Ann Arbor, Michigan, USA.|Neuroscience Graduate Program, University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: Brandon J
authors.initials: BJ
authors.lastname: Aragona
authors.affiliation: Department of Psychology, University of Michigan, Ann Arbor, Michigan, USA.|Neuroscience Graduate Program, University of Michigan, Ann Arbor, Michigan, USA.|Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: Joshua D
authors.initials: JD
authors.lastname: Berke
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D003657:Decision Making / Q000502:physiology*; D065786:Delay Discounting / Q000502:physiology; D004298:Dopamine / Q000378:metabolism / Q000502:physiology*; D055724:Electrophysiological Phenomena; D007858:Learning / Q000502:physiology*; D008297:Male; D017551:Microdialysis; D009042:Motivation / Q000502:physiology*; D009714:Nucleus Accumbens / Q000378:metabolism / Q000502:physiology*; D062308:Optogenetics; D051381:Rats; D020318:Rats, Long-Evans; D012201:Reward; D013997:Time Factors
chemical_list: D004298:Dopamine