eLife (Mar 2021)

Tonic firing mode of midbrain dopamine neurons continuously tracks reward values changing moment-by-moment

  • Yawei Wang,
  • Osamu Toyoshima,
  • Jun Kunimatsu,
  • Hiroshi Yamada,
  • Masayuki Matsumoto

DOI
https://doi.org/10.7554/eLife.63166
Journal volume & issue
Vol. 10

Abstract

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Animal behavior is regulated based on the values of future rewards. The phasic activity of midbrain dopamine neurons signals these values. Because reward values often change over time, even on a subsecond-by-subsecond basis, appropriate behavioral regulation requires continuous value monitoring. However, the phasic dopamine activity, which is sporadic and has a short duration, likely fails continuous monitoring. Here, we demonstrate a tonic firing mode of dopamine neurons that effectively tracks changing reward values. We recorded dopamine neuron activity in monkeys during a Pavlovian procedure in which the value of a cued reward gradually increased or decreased. Dopamine neurons tonically increased and decreased their activity as the reward value changed. This tonic activity was evoked more strongly by non-burst spikes than burst spikes producing a conventional phasic activity. Our findings suggest that dopamine neurons change their firing mode to effectively signal reward values in a given situation.

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