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Nat Neurosci. 2016 Jan;19(1):117-26. doi: 10.1038/nn.4173. Epub 2015 Nov 23.

Mesolimbic dopamine signals the value of work.

Author information

1
Department of Psychology, University of Michigan, Ann Arbor, Michigan, USA.
2
Neuroscience Graduate Program, University of Michigan, Ann Arbor, Michigan, USA.
3
Department of Chemistry, University of Michigan, Ann Arbor, Michigan, USA.
4
Department of Pharmacology, University of Michigan, Ann Arbor, Michigan, USA.
5
Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA.

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.

PMID:
26595651
PMCID:
PMC4696912
DOI:
10.1038/nn.4173
[Indexed for MEDLINE]
Free PMC Article

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