Mapping the estrous cycle to context-specific extinction memory.

In Pavlovian renewal paradigms, intact female rats have previously failed to exhibit renewal of appetitive behavior after extinction. However, when treated with exogenous estradiol, female rats exhibit robust renewal behavior. The current study aims to investigate whether the estrous cycle can influence renewal of appetitive behaviors and activity in brain areas known to support the renewal effect. We further aimed to examine whether the estrous cycle would similarly affect renewal of two different types of appetitive behaviors. We first establish that rats in the proestrous stage of the estrous cycle during extinction exhibit elevated renewal behavior compared with rats in either metestrous/diestrous stages, and only rats in proestrus during extinction training (but not during the renewal test) exhibit elevated renewal behavior. Furthermore, we show that this estrous cycle dependent effect on renewal only applies to the conditioned approach behavior toward the food delivery site but not the conditioned approach behavior toward the light cue associated with food delivery. Finally, we examined FOS activity within the prelimbic and infralimbic areas of the medial prefrontal cortex, the dorsal and ventral hippocampal formation, the paraventricular nucleus of the thalamus, the nucleus accumbens, and areas of the amygdala. Particularly in the hippocampus and amygdala, FOS expression which corresponded to the behavioral differences between groups was observed. Results from this study suggest that context information processing may vary as a function of endogenous female hormones across the gonadal hormone cycle and that encoding and retrieval of this information is accomplished in a state-specific manner. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Control of appetitive and aversive taste-reactivity responses by an auditory conditioned stimulus in a devaluation task: a FOS and behavioral analysis.

Through associative learning, cues for biologically significant reinforcers such as food may gain access to mental representations of those reinforcers. Here, we used devaluation procedures, behavioral assessment of hedonic taste-reactivity responses, and measurement of immediate-early gene (IEG) expression to show that a cue for food engages behavior and brain activity related to sensory and hedonic processing of that food. Rats first received a tone paired with intraoral infusion of sucrose. Then, in the absence of the tone, the value of sucrose was reduced (Devalue group) by pairing sucrose with lithium chloride (LiCl), or maintained (Maintain group) by presenting sucrose and LiCl unpaired. Finally, taste-reactivity responses to the tone were assessed in the absence of sucrose. Devalue rats showed high levels of aversive responses and minimal appetitive responses, whereas Maintain rats exhibited substantial appetitive responding but little aversive responding. Control rats that had not received tone-sucrose pairings did not display either class of behaviors. Devalue rats showed greater FOS expression than Maintain rats in several brain regions implicated in devaluation task performance and the display of aversive responses, including the basolateral amygdala, orbitofrontal cortex, gustatory cortex (GC), and the posterior accumbens shell (ACBs), whereas the opposite pattern was found in the anterior ACBs. Both Devalue and Maintain rats showed greater FOS expression than control rats in amygdala central nucleus, GC, and both subregions of ACBs. Thus, through associative learning, auditory cues for food gained access to neural processing in several brain regions importantly involved in the processing of taste memory information.