The Role of the Nucleus Reuniens of the Thalamus in Operant and Pavlovian Appetitive Extinction and Renewal
Harlan, Emery
Harlan, Emery
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Abstract
Contextual cues, background stimuli that constitute our environment, modulate learned behaviors (Bouton, 1993, 2019). Behaviors can be learned through operant conditioning, where a behavior produces an outcome, or through Pavlovian conditioning, where a stimulus predicts an outcome. One method to reduce unhealthy behaviors is through extinction learning, where an outcome no longer occurs; however, extinction is an especially context-dependent learning process, as demonstrated by the renewal effect, which is the return of a previously extinguished behavior when outside the extinction context. Our lab has previously shown that the medial prefrontal cortex (mPFC) modulates operant conditioning in a context-dependent manner (Eddy et al., 2016; Trask et al., 2017). Here, we investigated the nucleus reuniens (RE), a thalamic nucleus, which has strong reciprocal connections with the rodent mPFC (Vertes et al., 2015; Xu & S�dhof, 2013). Prior to all experiments, animals underwent stereotaxic surgery to have a guide cannula implanted into the RE. In Experiment 1, rats received daily training in Context A, where a behavior (lever pressing) was reinforced by an outcome (a food pellet). Animals were then extinguished in Context B, where lever pressing was not reinforced. Lastly, muscimol, a GABAA receptor agonist that temporarily inactivates neurons, was infused directly into the RE prior to testing in Context A and B. Animals that received muscimol exhibited reduced responding in Context A, but not B. In Experiment 2, we infused muscimol prior to operant extinction learning in Context B. Muscimol animals did not extinguish differently compared to control animals, but, when tested drug-free, they exhibited a heightened renewal effect. In Experiment 3, animals underwent Pavlovian appetitive training, where an auditory stimulus was paired with food. Muscimol, at test, did not impact responding in either context. Overall, the reuniens may have a different role in operant and Pavlovian appetitive extinction and renewal.
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Date
1/1/2026
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Graduate Student
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Oral Presentation
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Neuroscience Graduate Program
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College of Arts and Sciences
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Life Science