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.Reinforcer devaluation procedures are often used to assess cues' ability to guide behavior based on their access to a representation of the current incentive value of the reinforcer. For example, after tone-food pairings, the establishment of an aversion to the food reinforcer results in the spontaneous reduction of rats' learned food-cup approach responses to the tone, when it is presented later in the absence of food (Holland and Straub 1979). Thus, the rats' response to the tone is sensitive to changes in reinforcer value, despite no explicit experience of the tone together with the devalued reinforcer. Recent studies (for review, see Holland and Gallagher 2004) showed that this sensitivity of previously learned behaviors to subsequent alterations in reinforcer value demands function of a brain system that includes the basolateral amygdala (BLA) and the lateral orbitofrontal cortex (OFC).Previous devaluation studies examined changes in performance of learned responses preparatory to the receipt of food, such as food-cup approach. Here, we considered whether a learned cue for food would provoke consummatory responses that reflect the current sensory-hedonic aspects of food. In the absence of food itself, would a food cue provoke "liking" or "disgust" responses appropriate to the current...

In two experiments, rats received minimal (16) pairings of one auditory conditioned stimulus (CS) cue with a sucrose reinforcer, and extensive (112) pairings of another auditory CS with that reinforcer. After sucrose was devalued by pairing it with lithium chloride in some rats (Devalue groups) but not others (Maintain groups), taste reactivity (TR) and other responses to unflavored water were assessed in the presence of the auditory CSs alone. The minimally-trained CS controlled substantially more evaluative TR responses than the extensively-trained CS. Those TR responses were hedonic (positive) in the Maintain groups, but aversive (negative) in the Devalue groups. By contrast, food cup entry and other responses thought not to reflect evaluative taste processing were controlled more by the extensively-trained cue. These responses were reduced by sucrose devaluation to a similar extent regardless of the amount of training. The results suggest rapid changes in the content of learning as conditioning proceeds. Early in training, CSs may be capable of activating pre-evaluative processing of an absent food reinforcer that includes information about its palatability, but that capability is lost as training proceeds. Keywordsassociatively-activated event representations; contents of learning; devaluation; taste reactivity Considerable evidence shows that the contents of associative learning change over the course of extended training. Typically, learned performance is thought to be more flexible and goaloriented in early stages of training, but becomes increasingly automatic and less governed by its consequences with more extended training (e.g., Allport, 1937;Kimble & Perlmuter, 1970;Tolman, 1948.) Adams and Dickinson (1981) suggested that extended training may be accompanied by a shift from the control of behavior by outcome expectancies (stimulusreinforcer or response-reinforcer associations) to control by stimulus-response associations. Consistent with this view, several investigators have found that after extended instrumental training, responding is less sensitive to reinforcer devaluation (e.g. Adams, 1982;Bussey et al., 1996; but see Colwill & Rescorla, 1985;Holland, 2004), a primary indicant of the mediation of performance by outcome expectancies (Pickens & Holland, 2004). For example, Adams (1982) found that after small amounts of food-rewarded lever press training, devaluation of the food by pairing it with a toxin resulted in spontaneous reductions in lever pressing in the absence of food, whereas comparable food devaluation after extended lever press training left responding unaffected.Corresponding author: Peter C. Holland, 3400 North Charles Street, 222 Ames, Baltimore, MD 21218 USA, Voice: 1 410 516-6396, FAX: 1 410 516-0494, pch@jhu.edu. HL is now at the University of North Carolina, Chapel Hill and IA is now at Harvard University. NIH Public Access NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author ManuscriptOther evidence suggests that the content of learning may change more sub...