Appetitive behavioral traits and stimulus intensity influence maintenance of conditioned fear

Megan E Olshavsky,Marie-H Monfils,Hongjoo J Lee,Carolyn E Jones

doi:10.3389/fnbeh.2013.00179

Megan E Olshavsky, Marie-H Monfils + Show 2 more

Open Access

https://doi.org/10.3389/fnbeh.2013.00179

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Abstract

Individual differences in appetitive learning have long been reported, and generally divide into two classes of responses: cue- vs. reward-directed. The influence of cue- vs. reward-directed phenotypes on aversive cue processing, is less well understood. In the current study, we first categorized rats based on their predominant cue-directed orienting responses during appetitive Pavlovian conditioning. Then, we investigated the effect of phenotype on the latency to exit a familiar dark environment and enter an unfamiliar illuminated open field. Next, we examined whether the two phenotypes responded differently to a reconsolidation updating manipulation (retrieval+extinction) after fear conditioning. We report that the rats with a cue-directed (“orienting”) phenotype differentially respond to the open field, and also to fear conditioning, depending on US-intensity. In addition, our findings suggest that, regardless of appetitive phenotype or shock intensity, extinction within the reconsolidation window prevents spontaneous recovery of fear.

Highlights

When pairing a conditioned stimulus (CS) with a biologically significant event such as food, rats develop conditioned responses (CR)
In the case of light-food pairings, some rats develop both CS- and US-directed responses, that is, they orient/rear toward the light cue and approach the site of food delivery, while other rats develop only the food cup approach behavior. Because both groups exhibit an approach to the food cup and only a subset develops an orienting response to the light, we characterize these groups based on their conditioned orienting response to the CS and classify them as Non-orienters and Orienters, respectively
For the present study we first classified rats as either Orienters or Non-orienters based upon their expression of either CS-directed or US-directed responses during light-food pairings, we compared their behaviors within an open field task, tested whether expression of conditioned fear differs in rats that show robust cue-oriented responding and those that do not, and examined whether fear memory could be persistently attenuated in those groups using the retrieval+extinction paradigm (Monfils et al, 2009)

Summary

Introduction

When pairing a conditioned stimulus (CS) with a biologically significant event such as food (unconditioned stimulus, US), rats develop conditioned responses (CR). This result is important in light of the fact that many (Clem and Huganir, 2010; Schiller et al, 2010; Rao-Ruiz et al, 2011) but not all (Chan et al, 2010) labs have observed the persistent fear memory updating described in Monfils et al (2009), prompting a need to investigate the boundary conditions that surround this form of memory updating To this effect, for the present study we first classified rats as either Orienters or Non-orienters based upon their expression of either CS-directed or US-directed responses during light-food pairings, we compared their behaviors within an open field task, tested whether expression of conditioned fear differs in rats that show robust cue-oriented responding and those that do not, and examined whether fear memory could be persistently attenuated in those groups using the retrieval+extinction paradigm (Monfils et al, 2009)

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