Manipulating the revision of reward value during the intertrial interval increases sign tracking and dopamine release.
PLoS Biol. 2018-09-26; 16(9): e2004015
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1. PLoS Biol. 2018 Sep 26;16(9):e2004015. doi: 10.1371/journal.pbio.2004015.
eCollection 2018 Sep.
Manipulating the revision of reward value during the intertrial interval
increases sign tracking and dopamine release.
Lee B(1), Gentry RN(1)(2), Bissonette GB(1)(2), Herman RJ(1), Mallon JJ(1),
Bryden DW(1)(2), Calu DJ(3), Schoenbaum G(4), Coutureau E(5)(6), Marchand
AR(5)(6), Khamassi M(7), Roesch MR(1)(2).
(1)Department of Psychology, University of Maryland, College Park, Maryland,
United States of America.
(2)Neuroscience and Cognitive Science Program, University of Maryland, College
Park, Maryland, United States of America.
(3)Department of Anatomy and Neurobiology, University of Maryland, Baltimore,
Maryland, United States of America.
(4)NIDA Intramural Research Program, Baltimore, Maryland, United States of
(5)CNRS, Institut de Neurosciences Cognitives et Intégratives d’Aquitaine (INCIA,
UMR 5287), Bordeaux, France.
(6)Université de Bordeaux, INCIA, Bordeaux, France.
(7)Institute of Intelligent Systems and Robotics, Sorbonne Université, CNRS,
Recent computational models of sign tracking (ST) and goal tracking (GT) have
accounted for observations that dopamine (DA) is not necessary for all forms of
learning and have provided a set of predictions to further their validity. Among
these, a central prediction is that manipulating the intertrial interval (ITI)
during autoshaping should change the relative ST-GT proportion as well as DA
phasic responses. Here, we tested these predictions and found that lengthening
the ITI increased ST, i.e., behavioral engagement with conditioned stimuli (CS)
and cue-induced phasic DA release. Importantly, DA release was also present at
the time of reward delivery, even after learning, and DA release was correlated
with time spent in the food cup during the ITI. During conditioning with shorter
ITIs, GT was prominent (i.e., engagement with food cup), and DA release responded
to the CS while being absent at the time of reward delivery after learning.
Hence, shorter ITIs restored the classical DA reward prediction error (RPE)
pattern. These results validate the computational hypotheses, opening new
perspectives on the understanding of individual differences in Pavlovian
conditioning and DA signaling.
Conflict of interest statement: The authors have declared that no competing