Occasion setters determine responses of putative DA neurons to discriminative stimuli
Abstract
Midbrain dopamine (DA) neurons are involved in the processing of rewards and reward-predicting stimuli, possibly analogous to reinforcement learning reward prediction errors. Here we studied the activity of putative DA neurons (n=37) recorded in the ventral tegmental area of rats (n=6) performing a behavioural task involving occasion setting. In this task an occasion setter (OS) indicated that the relationship between a discriminative stimulus (DS) and reinforcement is in effect, so that reinforcement of bar pressing occurred only after the OS (tone or houselight) was followed by the DS (houselight or tone). We found that responses of putative DA cells to the DS were enhanced when preceded by the OS, as were behavioural responses to obtain rewards. Surprisingly though, we did not find a homogeneous increase in the mean activity of the population of putative DA neurons to the OS, contrary to predictions of standard temporal-difference models of DA neurons. Instead, putative DA neurons exhibited a heterogeneous response on a single unit level, so that some units increased and others decreased their activity as a response to the OS. Similarly, putative non-DA cells did not show a homogeneous response to the DS on a population level, but also had heterogeneous responses on a single unit level. The heterogeneity in the responses of neurons in the ventral tegmental area may reflect how DA neurons encode context and point to local differences in DA signalling.
Citation
Aquili , L , Bowman , E M & Schmidt , R 2020 , ' Occasion setters determine responses of putative DA neurons to discriminative stimuli ' , Neurobiology of Learning and Memory , vol. 173 , 107270 . https://doi.org/10.1016/j.nlm.2020.107270
Publication
Neurobiology of Learning and Memory
Status
Peer reviewed
ISSN
1074-7427Type
Journal article
Rights
Copyright © 2020 Elsevier Inc. All rights reserved. This work has been made available online in accordance with publisher policies or with permission. Permission for further reuse of this content should be sought from the publisher or the rights holder. This is the author created accepted manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at https://doi.org/10.1016/j.nlm.2020.107270
Description
This research was supported by a doctoral studentship to Luca Aquili from the UK Engineering and Physical Research Council.Collections
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