A specific olfactory cortico-thalamic pathway contributing to sampling performance during odor reversal learning
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A growing body of evidence shows that olfactory information is processed within a thalamic nucleus in both rodents and humans. The mediodorsal thalamic nucleus (MDT) receives projections from olfactory cortical areas including the piriform cortex (PCX) and is interconnected with the orbitofrontal cortex (OFC). Using electrophysiology in freely moving rats, we recently demonstrated the representation of olfactory information in the MDT and the dynamics of functional connectivity between the PCX, MDT and OFC. Notably, PCX–MDT coupling is specifically increased during odor sampling of an odor discrimination task. However, whether this increase of coupling is functionally relevant is unknown. To decipher the importance of PCX–MDT coupling during the sampling period, we used optogenetics to specifically inactivate the PCX inputs to MDT during an odor discrimination task and its reversal in rats. We demonstrate that inactivating the PCX inputs to MDT does not affect the performance accuracy of an odor discrimination task and its reversal, however, it does impact the rats’ sampling duration. Indeed, rats in which PCX inputs to MDT were inactivated during the sampling period display longer sampling duration during the odor reversal learning compared to controls—an effect not observed when inactivating OFC inputs to MDT. We demonstrate a causal link between the PCX inputs to MDT and the odor sampling performance, highlighting the importance of this specific cortico-thalamic pathway in olfaction.
KeywordsMediodorsal thalamus Piriform cortex Orbitofrontal cortex Olfaction Sampling
This work was supported by the National Institutes of Health – National Institute on Deafness and Other Communication Disorders (NIDCD) Grant R03DC014540 to E.C. and NIDCD R01DC003906 to D.A.W.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
All applicable international, national and/or institutional guidelines for the care and use of animals were followed. Animal care protocols and experiments were approved by the Nathan S. Kline Institute Institutional Animal Care and Use Committee and were in accordance with National Institutes of Health guidelines.
This article does not contain any studies with human participants performed by any of the authors.
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