RT Journal Article
SR Electronic
T1 A unified framework for dopamine signals across timescales
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 803437
DO 10.1101/803437
A1 HyungGoo R. Kim
A1 Athar N. Malik
A1 John G. Mikhael
A1 Pol Bech
A1 Iku Tsutsui-Kimura
A1 Fangmiao Sun
A1 Yajun Zhang
A1 Yulong Li
A1 Mitsuko Watabe-Uchida
A1 Samuel J. Gershman
A1 Naoshige Uchida
YR 2019
UL http://biorxiv.org/content/early/2019/10/15/803437.abstract
AB Rapid phasic activity of midbrain dopamine neurons are thought to signal reward prediction errors (RPEs), resembling temporal difference errors used in machine learning. Recent studies describing slowly increasing dopamine signals have instead proposed that they represent state values and arise independently from somatic spiking activity. Here, we developed novel experimental paradigms using virtual reality that disambiguate RPEs from values. We examined the dopamine circuit activity at various stages including somatic spiking, axonal calcium signals, and striatal dopamine concentrations. Our results demonstrate that ramping dopamine signals are consistent with RPEs rather than value, and this ramping is observed at all the stages examined. We further show that ramping dopamine signals can be driven by a dynamic stimulus that indicates a gradual approach to a reward. We provide a unified computational understanding of rapid phasic and slowly ramping dopamine signals: dopamine neurons perform a derivative-like computation over values on a moment-by-moment basis.