Effect of taste context and ambient context changes on successive negative contrast

Abstract

Rats shifted from 32% sucrose to 4% sucrose lick less than rats that experience only the 4% solution. Previous experiments have found this negative contrast effect to be reduced ("disinhibited") by the addition of a novel tone in the postshift period. In Experiment 1 of this paper, the negative contrast effect was enhanced when a novel flavor was added to the sucrose solution in the postshift period. In Experiments 2-4, changes in the ambient context, even changes sufficient to produce disruptions in licking, did not alter the degree of negative contrast. These results suggest that (1) rats compare rewards across substantially different contexts, (2) contrast may serve to enhance taste neophobia, and (3) a disinhibitory effect may be confined to the presentation of punctate, nontaste, novel stimuli within a familiar context. Rats shifted from a 32 % to 4 % sucrose solution consume less of the 4% solution than do animals that experience only the latter solution. Such "negative contrast" effects are pervasive in consummatory behavior, but the extent to which negative contrast is confined to the context in which different rewards are received has been little investigated. One study, which was concerned with the role of inhibition in contrast, showed that the introduction of a novel stimulus (a loud tone) concomitant with the shift led to a reduced contrast effect, but only on the second and subsequent postshift days (Lombardi & Flaherty, 1978).Other studies, using different contrast procedures in which animals regularly experienced two different reinforcers, showed that changes in the environment in which the animals received the reinforcers had relatively little effect on contrast (Flaherty & Avdzej, 1976;Premack, 1969). Similarly, recent studies in traditional learning paradigms have indicated that changes in conditioning context have relatively little influence on responding to a previously reinforced signal, although responding to a nonreinforced signal may be substantially impaired by context shifts (Bouton, 1986, in press;Kaye, Preston, Szabo, Druiff, & Mackintosh, 1987;Lovibond, Preston, & Mackintosh, 1984).The consummatory contrastprocedure is different from these traditional conditioning studies in that there is no explicit signal for the sucrose solutions other than the context itself. Since the animals presumably must compare the postshift reward with the memory of the preshift reward in order to show a contrast effect (e.g., see Flaherty & Lombardi, 1977;Gonzalez, Fernhoff, & David, 1973; This research was supported by NIMH Grant MH-40489 and by a Charles and Johanna Busch Memorial grant. Comments made by the reviewers substantially enhanced the paper. Correspondence may be addressed to Charles Flaherty, Psychology Department, Busch Campus, Rutgers University, New Brunswick, NJ 08903. Spear, 1967), the degree to which this memory must be associated with the preshift context is of some interest. The literature mentioned above suggests that rewards are compared across substantially different contexts w...

Within- and between-session variety effects in a food-seeking habituation paradigm

“…It is therefore possible that sucrose responding was enhanced by exposure to grain pellets on the alternate sessions because of a positive contrast effect—when organisms are exposed to a palatable food or flavor after exposure to positive but less palatable food or flavor, they may respond especially strongly to it (e.g., Flaherty, 1996). Interestingly, successive contrast effects have been demonstrated, as here, when the two incentives are presented in separate contexts and days (Flaherty, Hrabinski, & Grigson, 1990). A second type of contrast effect—negative contrast-- emerged when rats were briefly exposed to sucrose pellets and then switched to grain during the test session.…”

Contexts control negative contrast and restrict the expression of flavor preference conditioning.

“…However, other studies have failed to detect a role of contextual cues (Flaherty, Hrabinski, & Grigson, 1990). In the study by Flaherty et al (1990), a between-subjects design was used, in which one group received the exposure and test phases in the same context and another group received the phases in separate contexts. It is possible that such between-subjects designs lack the sensitivity to detect contextdependent effects.…”

“…There is some evidence that context cues do determine successive negative contrast (Daniel et al, 2008). However, other studies have failed to detect a role of contextual cues (Flaherty, Hrabinski, & Grigson, 1990). In the study by Flaherty et al (1990), a between-subjects design was used, in which one group received the exposure and test phases in the same context and another group received the phases in separate contexts.…”

Gustatory thalamus lesions eliminate successive negative contrast in rats: Evidence against a memory deficit.

“…Second, a change in time between baseline and probe trials could be viewed as a change in context that might affect probe trial performance. However, a change in the physical context (sufficient to disrupt licking) does not alter the degree of successive negative contrast (Flaherty, Hrabinski, & Grigson, 1990). That is, successive negative contrast is not context dependent.…”