Ziminski JJ1, Hessler S1, Sieburg MC1, Margetts-Smith G1, Crombag HS1, Koya E1
1Sussex Neuroscience, School of Psychology, University of Sussex, Falmer, BN1 9QG, United Kingdom
Animals utilize cues (e.g. smells) that predict food availability to seek out nutrient sources. If the same cue no longer predicts food availability during extinction learning, animals rapidly learn to inhibit their food-seeking responses. These Pavlovian cue-outcome associations are encoded by a minority of sparsely distributed, behaviourally-activated neurons coined ’neuronal ensembles’. Alterations in neuronal excitability underlie many learning and memory processes, but little is known about the excitability properties of neurons that are specifically activated during the retrieval of learned associations. In this study, we examined the excitability properties of behaviourally activated orbitofrontal cortex (OFC) and nucleus accumbens neurons following the retrieval of a sucrose memory (elicited by sucrose-associated cues in Pavlovian conditioned mice) or extinction memory. We performed whole-cell recordings on activated (GFP+) and non-activated (GFP–) neurons from the brain slices of Fos-GFP mice that express GFP in strongly activated neurons. Sucrose-associated cues recruited more GFP+ neurons in these areas compared to neutral cues. However, in the accumbens, but not OFC, GFP+ neurons were more excitable than their GFP– counterparts. Following extinction, this excitability difference was abolished in the accumbens, while GFP+ and GFP– OFC neurons continued to display no differences in excitability. These data indicate that sucrose memories are retrieved by recruiting distinct neuronal ensemble phenotypes in the OFC and accumbens, and that sucrose and extinction memories are represented in distinct neuronal ensemble phenotypes within the accumbens.
This research was funded by BBSRC (BB/M009017/1) and the University of Sussex Strategic Development Funds.