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Cyclic AMP-dependent plasticity underlies rapid changes in odor coding associated with reward learning
Journal article   Open access   Peer reviewed

Cyclic AMP-dependent plasticity underlies rapid changes in odor coding associated with reward learning

Thierry Louis, Aaron Stahl, Tamara Boto and Seth M. Tomchik
Proceedings of the National Academy of Sciences - PNAS, Vol.115(3), pp.E448-E457
01/16/2018
DOI: 10.1073/pnas.1709037115
PMCID: PMC5776964
PMID: 29284750
url
https://doi.org/10.1073/pnas.1709037115View
Published (Version of record) Open Access

Abstract

Learning and memory rely on dopamine and downstream cAMP-dependent plasticity across diverse organisms. Despite the central role of cAMP signaling, it is not known how cAMP-dependent plasticity drives coherent changes in neuronal physiology that encode the memory trace, or engram. In Drosophila, the mushroom body (MB) is critically involved in olfactory classical conditioning, and cAMP signaling molecules are necessary and sufficient for normal memory in intrinsic MB neurons. To evaluate the role of cAMP-dependent plasticity in learning, we examined how cAMP manipulations and olfactory classical conditioning modulate olfactory responses in the MB with in vivo imaging. Elevating cAMP pharmacologically or optogenetically produced plasticity in MB neurons, altering their responses to odorants. Odor-evoked Ca2+ responses showed net facilitation across anatomical regions. At the single-cell level, neurons exhibited heterogeneous responses to cAMP elevation, suggesting that cAMP drives plasticity to discrete subsets of MB neurons. Olfactory appetitive conditioning enhanced MB odor responses, mimicking the cAMP-dependent plasticity in directionality and magnitude. Elevating cAMP to equivalent levels as appetitive conditioning also produced plasticity, suggesting that the cAMP generated during conditioning affects odor-evoked responses in the MB. Finally, we found that this plasticity was dependent on the Rutabaga type I adenylyl cyclase, linking cAMP-dependent plasticity to behavioral modification. Overall, these data demonstrate that learning produces robust cAMP-dependent plasticity in intrinsic MB neurons, which is biased toward naturalistic reward learning. This suggests that cAMP signaling may serve to modulate intrinsic MB responses toward salient stimuli.
Multidisciplinary Sciences Science & Technology Science & Technology - Other Topics

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